Add documentation for crowddetector parameters and events.

Change-Id: I6ef6a3e62a249e1492206c89df9d04594957985f
Correct more typos in model.json documentation

Typos only surface as kmf-media-api javadoc and
other derived documentation is generated...

Change-Id: If9c6f9bc026a495f7aa3d15340dbdb55c78ee2b1