DDS — Ref-151 No_locally_duplicate_topics

The specification does not state what happens if the applcation
attempts to create multiple times a Topic with the same name

**PROPOSAL**

In section 2.1.2.2.1.5 state that calling create_topic muiltiple times
behaves as doing a lookup first with no timeout and if a Topic is
found then it compares the data-type & the qos specified as parameters
with those of the existing Topic.

State that if the comparison fails, than the operation return
PRECONDITION_FAILED.

State that if the lookup and comparison succeed then the reference
count to the Topic should be incremented such that the application
must call delete_topic as many times as it called create_topic and
directly lookup_topic for the local proxy to be deleted.

see below