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

This commit adds endpoints for browsing SWH snapshots. As origin-dependent
browsing and snapshot-dependent browsing are pretty similar, code
factorization has been performed trough the creation of a new
utility module swh.web.browse.views.utils.snapshot_context

Related T926
Closes T974

Closes T984

Closes T981

This new release fixes multi-line strings and comments highlighting bugs
(see https://github.com/wcoder/highlightjs-line-numbers.js/pull/22 and
https://github.com/wcoder/highlightjs-line-numbers.js/pull/30).

  - prefer to request file changes list asynchronously as it can take some time
    to compute for revision with numerous modifications

  - dynamically insert diff panels into the DOM

  - set the maximum number of displayed diffs to 1000

This commit adds the list of changed files in the revision
view but also the diffs (unified and side-by-side) of each
changed file.

Those new features are reachable from the "Changes" tab
in the revision view. Computation of file diffs will
be requested on the fly as the view is scrolled.

Regarding the diffs, they are only computed for textual
contents and diffs larger than 20 kB will not be computed
by default (the user can still manually request it
if needed).

Closes T921

Closes T972

Closes T971

  - persist cooking tasks list across browser sessions
  - enable to remove entirely or partially tasks from that list
  - ensure tasks list synchronization on browser tab focus
  - hide modals when replies of vault requests are received
  - fix progress bar color when a task failed

Closes T963