[Dashboards/Worklists/Export] Exporting a dashboard worklist widget will now respect the 'page' and 'limit' properties of the list.  This is far preferable to exporting thousands of rows, which can be done from the web API instead.  This also sets the stage for exporting contexts (with more included data), since we wouldn't want to return that much info for thousands of rows at a time.  The point of exporting dashboards (or pulling them from the UI) is to get a snapshot.
[Code Cleanup] Removed unused code in the 'customize' action of worklists.
[Code Cleanup] Fixed a bug in C4_AbstractView::_getDataAsObjects() where the DAO results should have been checking a nested array.
[Code Cleanup] The context for Message records was returning the wrong value for the 'is_broadcast' value (REST API, VAs, etc).
[Code Cleanup] C4_AbstractView::_getDataAsObjects() now preserves the proper sort order from the view.
[Code Cleanup] Updated several DAO::search() implementations for consistency with the standard.  The first argument should be $columns, not $params.
[Code Cleanup] Implemented a convenience method at Extension_DevblocksContext::getByViewClass() for looking up a context by a given worklist view class name.
[Code Cleanup/Contexts/Message] If a Message context is the top level in a chain (i.e. not nested) then it will allow lazy lookups for its parent ticket information.  This isn't required when nested because messages are only chained under tickets, which already provide their own information (otherwise you get a recursive lazy loader loop).
[Code Cleanup] Implemented all Calendar Recurring Event context labels/values.
[Code Cleanup] Custom fieldsets (cleaned up old references to 'custom field groups')
[Code Cleanup] Implemented Snippet context labels/values.
[Code Cleanup] Implemented some missing 'record_url' fields on contexts (calendar_event, message).
[Dashboards/Contexts/Export] Added the ability for context manifests to provide default 'expand' options for their lazy loader.  This makes it easier for functionality like exporting to be able to include all the relevant information.  For instance, tickets and messages generally need to expand address information to be useful, etc.
[Code Cleanup] Implemented 'calendar_' lazy loading from calendar event contexts.
[Dashboards/Workspaces] Exporting worklist widgets from dashboards and REST API (JSON/CSV) uses context info rather than search results (more detailed, more human readable, and includes linked records).
6.4-rc checkpoint