Update jQuery Cookie Plugin to 1.4.0
Wrap toolbar.js in AMD define() if it exists
whitespace-only

convert tabs to spaces
Change how JS libs are loaded

This change makes Django-Debug-Toolbar use the existing version of jQuery
on the page if one exists, and only loads jQuery if it isn't already loaded.
It also explicitly loads the jQuery cookie plugin and the toolbar script
as separate files. Finally, we are no longer compressing/minimizing scripts;
this is for debug purposes, and presumably will not be served in production.
Addressing review comments
load jQuery with document.createElement instead of document.write

to satisfy integration test
Temporary workaround for a regression introduced by #440.
Avoid some implicit global lookups.

They made it impossible to preserve panel data after the end of a
request.
Load the content of panels dynamically.

This should drastically reduce the overhead of the browser toolbar when
a page has a complex template structure or many SQL queries.

This change is backwards-incompatible for third-party panels because it
changes the signature of __init__.

The JavaScript could probably be improved; I'm outside my comfort zone.
Improve regression test added in 8525bfc7.

Refs #422.
Invalidate cached list of panels during tests.
Prevent some tests from succeeding by accident.
Move a test specific to the profiling panel in its module.