Add information about Mconf-Mobile in the join_mobile view, refs #807

Similar to the information added to the invite view.
Use new locale to display success message when changing languages. Fixes #756
Mark messages as read when user clicks to read more fixes #630
Translate string when attachments are empty. Fixes #859
Use correct titles for tags in attachments, fixes #854
Developed a new way to catch, and handle, exceptions raised by the station when a user try to access a non authorized space.

fixes #815
Better rescue from Station::NotAuthorized as station is updated

Now station will always throw Station::NotAuthorized so we have to treat it
and render the pages we need to.
Spaces and routes inside spaces will redirect to the new join request page
if the user is trying to *see* a page. If he's trying to do something else
(e.g. update a post he can't updated), he will still get a 403.
Now all the links in the list of spaces will redirect to space's home page. The treatment for authorized users will be done by station.

Fixes #816
Refs #815
refs #809
Logic is done.
Next step is create some tests for the application_controlller.
refs #809
Created tests for function bigbluebutton_can_create?
I'll do some tests for the route as well, depending on what data the user inputs on form.

cherry-pick aa364f388a

Conflicts:
	spec/factories/bigbluebutton_room.rb
refs #809
created tests for the bbb room controller
checks if the user can start a meeting or not depending if he's the owner or not of that room

cherry-pick 4057a6e0e2
Refactor the tests for #809

The same tests, just reorganized.
Complements ef138b788e55 and bc709b9910.
Update bigbluebutton_rails, refs #809
Now the page that list the recordings of a private space is available only for members of the space.

fixes #865
Translate fields and correct private message forms. Fixes #763
Always redirect to referer when messages fail to be created, refs #763

It was redirecting to the referer when there was no `receiver_id` in the
params, but rendering the view index when there was a `receiver_id` but
something else was failing.
Now it always redirects to the referer and sets a more detailed flash message.
Update locales, refs #763
Added more tests for invited behavior. refs #820
Added information about invited role. fixes #820
Set 'member' as a default role in invitations to spaces, refs #820