load scripts as a single file

The theme doesn't need to know what libraries Numbas uses now!
Might be a bit quicker to load, as well.

Need to check that extensions work, and to update the other themes
Merge branch 'master' into onescriptfile

Conflicts:
	runtime/scripts/knockout/knockout.js
update worksheet theme to work with combined script file
Merge branch 'master' into onescriptfile
collect all CSS files into one