DDS — DDS ISSUE# 38] Allow application to install a clock

Ref-114 Behavior_of_instances_when_deleting_datawriter

What happens when an application deletes a datawriter? Do all
registered instances become unregistered? What about samples that may
have been written but not propagated to remote readers?

There are two possibilities:

Approch1 behave as if the application had crashed with regards to the
readers. The application should have been explicit about the contained
entities (e.g. unregister/dispose) before deleting the writer.

Approach2 handle it as any deletion of a container entity. It is a
pre-condition error if it has any registered instances and the entity
is not deleted. But also we provide helper operations on the
DataWriter to unregister_all_instances() and dispose_all_instances().

**PROPOSAL**

Use Approach2. Its more explicit and less error-prone.

Also say that the infrastructure is not required to immediately
release the resources before returning from the delete but can keep
them around for a while until is properly has a chance to clean up its
state, inform remote nodes, etc.

see below