The properties exposed by the ActiveMQ pooled connection factory are
quite specific and I felt it was arbitrary to expose some and not others.

However, the number of connections and the timeouts seem the most useful
so they have been kept and a `configuration` nested namespace can be
used to configure any additional settings.

The core properties have been renamed to be less "raw" and more compliant
with the structure of other properties. The documentation on fields has
also been aligned.

Closes gh-5372