Move drop hover trigger to DropView

* Encapsulation; belongs to the DropView.
Fix references to missing Controller_SwiftRiver::accountServce

sigh
Modals: Allow multiple secondary views

Views are stored in a stack to allow more than one child views.
Removed themes/default/views/pages/river/settings/channels.php

* Old settings page no longer used.
Added an abstract service class

Reuse +1
Drop_Base not Drop_Container
Refactor dashboard content js

* Allow easier addition of other asset types.
* Event driven; rely on Backbone events
Form management implemented

* Create, Update, Delete forms and related implemented.