show source in advanced menu
Merge branch 'develop' into move-tools-to-top
move footer tools to advanced menu

debatable, but at least we keep the clutter in one place
rename open-from-github once again

where will it end.
put publish notebook in advanced menu

generalize checkbox menu item (however ugly) into ui_utils
don't show "notebook assets" when there are none
put github id into advanced menu
eliminate notebook properties accordion
setup show source in shell
artifacts
add show source option to view.html advanced menu

move show source checkbox deeper, into controller
properly wrap changes to show source, to update checkbox
view.js was improperly calling Notebook.hide_r_source directly

closes #154
artifacts