Remove the download restriction on that endpoint when no mimetype
is associated to a content or when a content is not detected as
textual.

Closes T1314
Closes T1315

  - highlight a whole row when hovering on it with mouse pointer

  - make a whole row a link in most cases for better navigation

Previously in history views, revisions were ordered according to the
BFS traversal of the revisions DAG.

This commit adds three new ordering type modifying the history display:

  * Committer date ordering: revisions are displayed in reverse chronological order
    of their commit date

  * DFS: revisions are ordered according to the DFS traversal of the revisions DAG

  * DFS post: revisions are ordered according to the DFS post traversal of the
    revisions DAG

The four types of revisions ordering can be easily switched through the UI.

Closes T1026

  - handle all possible release target types

  - add link to target in releases list view

  - slighlty refactor html templates

Closes T1309

When encountering such a case, do not return a 404 error but
rather display to the user that it is an empty snapshot.

Closes T1303

Closes T1304

Closes T1301

Related T1247

Related T1261

Closes T1288

Related to T1261.

In order to gain more display space and have a better design and browsing
experience, the following actions have been taken care of:

  - fix min-height computation of div.content-wrapper

  - remove some bootstrap cards and leverage the use of the top navbar
    to display the info regarding the type of object currently browsed

  - uniformize table stylesheets

  - remove some useless borders for a cleaner design

  - increase the number of displayed origin search results from 20 to 100

  - factorize some html templates

  - also fix some navigation issues

Closes T1272