Related T1061

  - prefer to display a smaller spinner in the left of the search panel
    header instead of a big one at the center of the screen

  - clean the search results table when performing a new search

Closes T1056

This commit adds query parameters to some context indedependent views
in order to add origin info.

Closes T1055

Closes T1054

Value was turned to True in commit rDWAPPS0bc0934bca8ee36bcb1e2f8ef57c951fd5c6acca
so turn it back to False.

Closes T1053

Summary:
The tests now depend on webpack being built, so do that before running make
test.

The devserver depends on migrations being run, so do that as well.

I'm not entirely sure the migration part is the right thing to do, but at least
with the webpack part, running the tests will do reasonable things.

Test Plan: make test still works

Reviewers: anlambert, #reviewers!

Differential Revision: https://forge.softwareheritage.org/D320

  - Add a button in the top left part of origin context views to easily
    reach visits reporting view

  - Add a button in the origin visits reporting view to easily browse
    the latest snapshot

This allows to leverage client level cache efficiently and invalidate
already cached assets when source have changed.

When there is only one full visit, the last full visit link
was not displayed.

Url of type /browse/origin/(origin_type)/url/(origin_url) now redirects
to the display of the latest archived snapshot for the given origin
instead of its visits reporting.

Origin visits reporting are now available through the following url
/browse/origin/(origin_type)/url/(origin_url)/visits or by clicking in
the topmost link when browsing the archive in an origin context.

Closes T1049

This commit replaces navigation through tabs for the browse main menu
(search/help/vault/browse) by assigning a dedicated page and url to
each menu entry.

This prevents interface flashes when loading any browse page as
previously the search interface was always displayed first before
switching to the requested tab.

This commit fixes bad license name in some Python files (swh-web is
AGPL not GPL) but also adds license header in static assets related
source files (html, js, css).

As Bootstrap 3.x is no longer maintained, migrate swh-web frontend to
the last major version: 4.x (current version is 4.1).

This induces the following changes:

  * migrate from 3.x css classes to 4.x css classes

  * leverage Boostrap sass variables overriding in order to generate
    custom css for swh-web

  * use the free AdminLTE Bootstrap theme for its clean design
    (see https://github.com/almasaeed2010/AdminLTE/tree/v3-dev)

In adition to that migration process, some cleanup and prettifying
have been performed on Django HTML templates.

Related: T1032

See https://github.com/npm/npm/issues/17379#issuecomment-359832471

Close D311

In development mode, prettify all HTML generated by Django to ease debugging.

In production mode, minify all HTML generated by Django to reduce the amount
of data to send to clients.

This commit improves frontend development for swh web applications
by setting up a static assets pipeline using the module bundler tool
webpack. It enables to organize frontend development into logical
modules and then package those modules into multiple bundles that
will be loaded when required by client browsers.

This induces the following changes (see updated README):

  - node.js is now a requirement for developping swh-web

  - all static assets dependencies (javascript libraries, stylesheets,
    web fonts) are now managed and retrieved using npm.

  - all static assets will now be served through our web server

Regarding the webpack workflow put in place, it offers the following
features:

  - automatic linting of custom javascript and stylesheets in order
    to have a consistent code style and avoid bad pratices

  - the possibility to use es6 syntax and recent javascript features
    (like async/await) through the use of babel (es6 to es5 transpiler)

  - leverage the use of webpack-dev-server in development mode
    in order to automatically reload web applications in the browser
    when modifying source files

  - in production mode, minify javascript and stylesheets but also
    perform dead code elimination in order to reduce bundle sizes and
    thus optimize the amount of data to serve to the clients.

Closes T1006

Closes T1001

This commit improves the view displayed by reaching the
/browse/origin/(origin_type)/url/(origin_url)/ endpoint
through a wayback machine like interface.

Relevant links to latest full visit, first full visit and last visit
for the origin are first displayed.

The full SWH visits history is then available through three visualization
components:

  - a stacked histogram displaying the amount of visits by month
    (visits are stacked by status) and enabling to filter the visits
    according to a specific year

  - a calendar view giving visit details for each day of a
    selected year

  - a raw visit list for the selected year

Visits can also be filtered the following ways:

  - full visits pointing to different snapshots

  - all full visits

  - all visits

Closes T959
Closes T961

see https://github.com/twbs/bootstrap/issues/21830 for more details