Pre-populate the manage feeds form from db only on a GET request

This avoids duplicate population, one from the database and one from
POST data. Previously it would have populated the form, with information
from a database lookup, only to replace it with POST data, if both were
present.
Add core flash messenger template

This will be used to display flash messages in a Twitter Bootstrap
compatible manner.
Display flash message on attempt to edit non-existent feed record

If a user attempts to edit a non-existent feed record, they're redirected
to the normal add form along with displaying a flash message, so they
know what happened.
Merge branch 'feature/add_flash_messenger_support' into develop
Add support for displaying error (flash) messages
Redirect and display message on attempt to delete non-existent feed

If an attempt is made to delete a non-existent feed, the user is
redirected to the index action and shown a message saying the feed
wasn't found.

It might be simpler to add a "record exists" type function instead of
attempting to load the entire record?
Merge branch 'feature/add_flash_messenger_to_delete_feed' into develop