Rename, refactor, and expand collection view traits.

Switch to classes from structs to share a base
class.

Rename file to limit its potential future size.

Add new AutoReloadDataTrait.
Refactor Months screen with AutoReloadDataTrait.
Add AutoReloadDataTrait to Day screen.

Partially allows proper Day screen updating on
Event screen save.

Minor reorganization and fixups included.
Add day-events accessor to EventManager.

This will allow access to an up-to-date day-events
collection.

Refactor date helpers into NSDate extension.

Minor reorganization included.
Switch to directly using EventManager as Day screen data source.