API for querying remote daemon config. #4778

This adds a new class to the python bindings, RemoteParam.
A RemoteParam object (initialized with a ClassAd containing
at least the MyAddress attribute) behaves similarly to the
Param object and a python dictionary.

One difference is that, on access, the remote daemon is
queried for configuration instead of doing this at objection creation.
Merge branch 'master' into V8_3-gt4778
Allow the RemoteParam class to set runtime configs. #4778

Includes unit tests.  Note that daemons must be explicitly reloaded
after setting the config and that unsetting a configuration parameter
changes the value to "Not defined".
Improve unit test coverage for remote params. #4778

Also includes version history.
Merge branch 'V8_3-gt4778'