#ue4
- Added stacking rules and tests.
- Changed effects with a period to execute on the next tick instead of instantly and updated gameplay effect tests to account for these changes.
- Changed ticking of active effects to allow effects to execute multiple times in a single tick.
- Make sure we're cleaning up actors between gameplay effect tests
#codereview Dave.Ratti
[CL 2055992 by Fred Kimberley in Main branch]
