Make init.sage work

Ideally, this would later be changed to use `attach` again.
Cache bust canvas3d so they reload properly
dummy translation functions N_ and nN_ and js localization refactor
nN_ made accesible to localization.js
Allow new 500 message to be localized
Merge pull request #314 from kcrisman/tinygettextfix

Allow new 500 message to be localized
fix plural translations in javascript
Merge pull request #312 from migeruhito/dummy_gettext

Dummy translation functions and two cases of use
Merge pull request #284 from kcrisman/canvas3dcachebust

Cache bust canvas3d so they reload properly
Merge pull request #267 from kcrisman/initfix

Make init.sage work