Bundle all javascript and CSS

[martinRenou]

• Removes IE dependencies
• Bundle Admin-lte and its dependencies in one javascript file (sharedDependencies.js) loaded both by the admin page and the user page.
• Bundle Admin-lte and its dependencies in one CSS file (sharedDependencies.css) loaded both by the admin page and the user page.
• Creates a new directory "dist/files" which contains all the files (fonts, images...) needed by the CSS.

It remains google analytics javascript, but it is loaded via https and depends on the backend.

Closes #484
Closes #485

[codecov-io]

Codecov Report

Merging #510 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #510   +/-   ##
=======================================
  Coverage   95.25%   95.25%           
=======================================
  Files          88       88           
  Lines        3960     3960           
  Branches      248      248           
=======================================
  Hits         3772     3772           
  Misses        137      137           
  Partials       51       51

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e623f7b...4ee5a32. Read the comment docs.