* Playbook
* TaskInclude

Also reworking tests to cut down on the number of patches required
by sub-classing the DataLoader() class and reworking the base object's
structure a bit to allow its use

* added ability to set parents (will be used when the deps are loaded)
* added role caching, so roles are not reloaded needlessly (and for
  use in detecting when roles have already been run)
* reworked the way metadata was stored - now individual attribute fields
  instead of a dictionary blob

* using inspect module instead of iteritems(self.__class__.__dict__, due
  to the fact that the later does not include attributes from parent
  classes
* added tags/when attributes to Base() class for use by all subclasses
* removed value/callable code from Attribute, as they are not used
* started moving some limited code from utils to new places in v2 tree
  (vault, yaml-parsing related defs)
* re-added ability of Block.load() to create implicit blocks from tasks
* started overhaul of Role class and role-related code