Tranlate occurences of 'kcal' and 'g'

See #94
Remove remove browserid.js

This file is not needed anymore with the last version of django-browserid
Fix urls for demo entries, registration and login
Clean up and simplify some translated strings

To make translating the application faster and easier for translators, the
strings used in the different views have been reduced or replaced by a generic
one.

See #94
Remove unnecessary parenthesis
Simplify code to check for ownership of days
Fix namespace of weight unit links