Restore GatewayQuiz timer functionality.

The timer on time limited quizzes were't showing up since it can't find
gateway.js anymore. Some investigation reveals that gateway.js was placed into
the 'htdocs/js/delete-me' directory during js reorganization. I've moved it
into the new page-specific js location which is in
/htdocs/js/apps/GatewayQuiz/gateway.js.

Also fixed it for math3. Did not fix it for the other themes, not sure if
they're relevant anymore?
GatewayQuiz timer initialized using jquery.

Use jquery's .ready() to activate the quiz timer once the page has finished
loading. Needed to import jquery in math3.
GatewayQuiz, fix knowl.js import.

Looks like knowl.js was also moved during the js reorganization and now lives
at /htdocs/js/vendor/other/

The import for knowl.js was being written by the GatewayQuiz content generator,
I've moved it into the gateway quiz template instead.

Not sure what exactly is using knowl.js
GatewayQuiz, remove generation of extra div & td.

There is an edge case where an empty gwMessage div is generated when there are
no recorded submissions & the test has expired. Fixed by moving the gwMessage div generation code into the if statements that prints the actual messages.

If there are multiple messages to show after checking a response, an extra td
is generated for every message after the first. This td would've been fine if
message rows don't generate the label td after the first message like how all
the other result rows are, but it generates the message label for every
message, so we end up with an extra blank td.
Spruce up the CSS for gateway quizzes.

Mainly just some rounded corners, drop shadows on the boxes, and adding whitespace to various elements. Also lightened the question background for better readability. The 'Print Test' and 'preview problems' links were styled into buttons.

Header now using new css header.

Adjusted footer to be the same as the system template.