DDSPSMC11_ — Instance handle constructor for TopicInstance should be deleted.

The dds/topic/TopicInstance object is used as a holder for both a sample, and the instance handle to its corresponding instance. There are operations on the DataWriter that accept a TopicInstance as their parameter.

However, it is possible to instantiate a TopicInstance without sample, by using a constructor that only accepts an instance handle. It is unclear what the behavior of the write operations should be in case they receive a TopicInstance without corresponding sample.

I therefore propose to either delete the constructor that accepts only an instance handle, and remove the key_value() function that accepts TopicInstance as input parameter (it is already overloaded by another key_value() that accepts an InstanceHandle) or otherwise define an exception when passing a TopicInstance without sample to a write() operation.