Bump version to 0.0.49
Documentation clean-up/additions
Finally resolve strange naming inconsistency
Basic clarification of some required files
Overhaul of "participant" file/class hierarchy

Renamed a bunch of core components, so this will break existing
implementations - good thing we're not even at 0.1.x, yet, for some
reason.
Introducing the EntityInteractor participant!

The entity interactor lets you call methods on the process's entity,
with or without arguments, and optionally store the return value in
a workitem field.