Remove topbar/hide button and other excess HTML.

These features are unnecessary to the shell and should be taken care of
in the page the shell is embedded in (i.e. display: none). In the shell,
the code just becomes maintenance cruft.

Note that the CSS is now broken and will be fixed in the following
commit.
Fix up CSS from topbar removal.

Additionally, removed excess/unnecessary attributes to make it as lean
as possible. Tested on Firefox and Chromium.