Properly import PDO classes in the DB class.
Have sensible default for ID fieldname in DataAccess entity trait
Expose afterLoad function for use when loading entity collections.
Renamed a couple of instance variables in the Database entity trait.
Added the ability to set whether or not an object is new via public methods

This is for use with loading entity collections.
Various bugfixes for database entity traits.

- Use actual functions that exist for function calls.
- Properly refer to classes such as PDO and Exception that are in the
  global namespace.
- Properly refer to the DB instance variable.
- Don't import dependent traits. This means that an entity that wants to
  use DatabaseLoad or DatabaseSave (or both) must manually import
  DataAccess and Database as well. This is because you can't import
  multiple traits that all import the same trait. PHP blindly assumes
  you want that trait twice, rather than just resolving it sanely like
  you would want to with class composition.
Initial commit of entity collection traits.

A lot of work has gone into these. They are as yet untested though,
unfortunately.