DDS15 — When using GROUP access scope presentation QoS, allow for read/take outside of begin_access and end_access block

Problem: The DDS specification (section 2.2.2.5.2.8) does not allow access to the DDS cache when the application wants to access data, but does not care about the order across Data Writers.

Proposed Resolution:
When using GROUP access scope, allow both access patterns and do not return PRECONDITION_NOT_MET
error code when called read, take, etc. without first called begin_access.

Note: This also allows portability for applications which do not care about the order across topics.