Refactor Gruntfile
Add git branch name grunt version task
Add branch name to about section in helpPanel
Capitalize date string in en i18n file
Merge pull request #474 from latin-language-toolkit/branch_names_in_versioning

Branch names in About section
Add ability to skip auth in specific modes

The configurator knows the general active mode and exposes a function
to check for it.
It's also the only place to instantiate Auth instances.

Auth instances can now be configured with an array of `skipModes` -
modes where the authentication routine is circumvented.

The configurator passes the mode function to the Auth instance, so that
it can check if authentication is required or not.

Closes #458