Remove some no longer used sidebar links

This goes with the massive purge of content from the user-docs repo
[endlessm/eos-shell#3909]
Revert "style: remove black content sidebar"

This reverts commit 6306df14c91b6ba74d42999b6c82ee93c50d9e6b.
Css changes from Mac and co

Some last minute style fixes to put us a bit closer to our actual
designs.

They have been working on a wip branch, just squashed the many
commits there together removed the test html and css files and
committed what was left
Remove -moz css properties

Added in the previous commit. We don't care about firefox rendering
our stuff
Fix lato fonts

It was set up for viewing in a browser I guess. The way to specify
lato in webkit gtk is a bit different and was commented out
Include new assets in the makefile

So they really show up and install
Usability style fixes

All links have a hover state (some did not), category links bigger
then the subtopic links underneath
Improve media player

Sizes to the whole window and stays centered
Placeholder theme for tutorial button

Not to any spec, but just an adhoc one to make the link a little
more obvious

[endlessm/eos-shell#3909-2]
Merge pull request #8 from endlessm/shell/3909

Remove some no longer used sidebar links
Merge pull request #9 from endlessm/shell/3909-2

Shell/3909 2
Add video tutorials to the sidebar
[endlessm/eos-shell#3909]
Merge pull request #10 from endlessm/shell/3909

Add video tutorials to the sidebar
Translation for "Video Tutorials"

[endlessm/eos-shell#3909]