Filter by channel_ids

* Filter key changed to channel_ids from channels
Filter drops list by read/unread state
River Collaborators

* Add/Remove collaborators implemented
* Modify pending ui changes for editor/readonly selection
Merge branch 'integration-dev' into rivers-ui-dev
Bucket collaborators implemented
Visual feedback

* Show loading message when creating, updating or deleting
rivers/channels takes too long.
* Show a system message on failure/success.
Masonry fix

* Increase the width of the drop "container" to 31.25%
UI: Revised "Add collaborators" prototype
Merge branch 'integration-dev' into buckets-ui-dev

Conflicts:
	application/classes/Controller/User.php
	application/classes/Service/River.php
	modules/SwiftRiver_API/classes/SwiftRiver/API/Accounts.php
	modules/SwiftRiver_API/classes/SwiftRiver/API/Rivers.php
Add links, tags to river and bucket drops

* Additional links, tags etc are specific to drops within a specific
river or a bucket

* Renamed Controller_Drop_Base to Controller_Drop_Container and
made it an abstract class with methods that must be implemented by
all classes that extend it