Initial modifications to change the rooms permissions in spaces.
Changed the web conference permissions in spaces

Formerly the permissions of the spaces were as follows:

 - All members of a space will be moderators in its web conference room;
 - All members of a space can start a web conference in the space;
 - All members of a space can stop a web conference in the space.

Now this is the new set of permissions:

 - Only administrators of a space and the person that started the web conference will be moderators;
 - All members of a space can start a web conference in the space;
 - Only administrators of a space and the person that started the web conference can stop the conference in the space.

Required the new version of the bigbluebutton_rails gem.

Refs #1148
Refactor attachments

Conflicts:
	db/schema.rb
Store attachments where logos are stored
Migrate old attachments
Remove lots of dead code in attachments and library dependencies
Make multi download and remove work again for attachments, refactor controller
Removed a bunch of code from attachments controller/model
Make tests for attachments pass. They're mostly abilities tests
Remove unused gems and files
Remove unused fields from attacments
Remove many unused gems
Remove old file with references to fcbk
Remove station and attachment stuff
Redo some queries in controllers to pass tests
Correct space count in manage controller
Fix missing partial destroy_space in manage/spaces
Add missing shib_env_variables to sites/edit and sites/show

Also improved some strings related to shibboleth and the account association
view.
Update mweb_events and several small improvements when showing events
Unify css for visibility of spaces and events

Different classes were being used. Now it's always "resource-visibility".