…o HTML5.

Signed-off-by: Norv <a.w.norv@gmail.com>

…p and Search.template.php)

Adds a skip navigation link to index.template.php (basic a11y addition for keyboard users).

Removes the #outer_container div from GenericControls.template.php (wasn't doing anything useful).

Adds a slight menu tweak to admin.css (which is still a mess otherwise, but ignore that for now).

Fixes dodgey old language strings in Install.english.php (elkarte#584)

Signed-off-by: Norv <a.w.norv@gmail.com>

NOTE: Since the max-height appeared essential, I put it in script.js
so that people wouldn't remove it and then wonder why things broke.
Other CSS was moved the other way, from script.js out to index.css.
Removed catbg class from the heading, as it will be deprecated, and left it as plain h3.
Also, added title to close link for a11y. @todo - Really should have a proper language string.

Signed-off-by: Norv <a.w.norv@gmail.com>