starting to rework the editable question view
add bootstrap files
starting on parts
Merge branch 'master' into bootstrap

Conflicts:
	editor/templates/base.html
	editor/templates/question/editable.html
move variable delete button
Merge branch 'master' into bootstrap
starting on question parts
Merge branch 'master' into bootstrap
still working on parts
more parts, more styling
fix removal of function parameters

When creating a function on page load, the FunctionParameter constructor was being passed `this` (which happened to be the browser window object) instead of a reference to the function model.
fixes #122
update JME scripts
update JME scripts again
Merge branch 'master' into bootstrap
bootstrap: choices for 1_n_2 parts; input labels are clickable
bootstrap: m_n_2 and m_n_x parts

I've just plugged in the old choices/marks matrix thing for m_n_x. I'll have another look at it later.
bootstrap: gaps and steps in part list
bootstrap: question tags and extensions
Merge branch 'bootstrap' of github.com:numbas/editor into bootstrap

Conflicts:
	editor/static/css/question/edit.css
add a header for the question name input