GUAC-605: Add reconnect countdown

This change generalizes the status dialog and notifications into a single directive ("guacNotification") which is included and styled differently depending on usage. The new "guacNotification" directive provides support for automatic countdowns until some arbitrary default action, defined by a callback.

Sorry for the sheer enormousness of this PR. A good portion of the visible diff will be the additional messageformat.js library and corresponding MessageFormat interpolation plugin for angular-translate.