RTPS: added new PIDs and included minor improvements
- (Updated) Fixed code review issues
- (Updated) Fixed whitespaces and code review issues
- Representing now some NTP times as duration (not as date)
- Added some vendor specific PIDs (RTI)
- Added dissect_APP_ACK_CONF, dissect_APP_ACK and
  dissect_HEARTBEAT_VIRTUAL
- Added is_discovery to dissect_serialize_data to avoid malformed
  packets when using mutable types (Wireshark assumes serialized
  data with CDR-PL encapsulation is always discovery data, what
  is not true when using Mutable types)

Change-Id: I491750d95b12f386c41d7de4ae7e280781efa375
Reviewed-on: https://code.wireshark.org/review/3836
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>