[api] fix handling of files inside _project container, add testcases
[api] replace rails 2 code with rails 4 code
[backend] route all notifications through the src server's notify() function
[backend] implement lastnotifications streaming service

TODO: implement deletion of already sent events
[backend] add a route to the backend to notify plugins

As multi action support needs nested data structures, make use of JSON
[api] remove the configuration option for multiaction_notify_support

The plugins get all the informations now and decide for themselves what
they filter
[webui] add basic functionality to edit user subscriptions