Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/39798

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/39513

This moves away from storing in a single array just to render the table.
It now stores in a multi-dimensional array/object type where each entry
in the array can have its own tree. This makes storing the data for
future feature a little easier as there is only one way to store the
data.

Previously to insert a directory the code had to insert the directory
& then the file at the right point in the array. Now the directory
can be inserted anywhere & then a file can be quickly added into this
directory.

The rendering is still done with a single array, but this is handled
through underscore. Underscore takes the array & then goes through
each item to flatten it into one. It is done this way to save changing
the markup away from table, keeping it as a table keeps it semantically
correct.

hover animations for award buttons, buttons, dropdowns, rows in file list, links, navigation tabs, labels

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

As discussed in #15667.