Resolved JERSEY-2047: jersey.ent file clean-up.

- Consolidated naming.
- Removed entity definitions with a single, local usage.
- Moved some of the topic-specific entity definitions into the chapter where these are used.
- fixed minor issue with ContentEncoder entity name.

Change-Id: I1dd1fc799176959f297246bbba6aea71e44c14fe
Signed-off-by: Marek Potociar <marek.potociar@oracle.com>