Add EntityPortalEvent

Need to determine how/if to "share" PlayerTeleportEvent.TeleportCause
with EntityPortalEvent
Added ability to allow for adjustment of arrival parameters for entity
Added convenience constructors for Trajectory.
Added CardinalDirection enum
Relate CardinalDirection as a filter to BlockFace
Clarify TravelAgent.adjustArrival usage
Add conversion from BlockFace to CardinalDirection
Remove out-dated @throws
Remove Cardinal Direction
Validate not throw
Revert TravelAgent change
Add EntityPortalExitEvent
Clarify event usage
Minor clarification adjustments
Clarify portal event descriptions