Clean up serialization for REST APIs.  Get rid of the jackson converter module and just use annotations everywhere when appropriate.  There may still be a desire for something like the jackson converter module but it didn't really mesh with the plugin system, and the annotations work nicely.

Initial support for OVS-style role request messages and maintaining connections with switches in a backup role [#23366119].
Added REST API to get/set the current role of the controller [#2336329].
Added simple health check REST API [#23364299].
Fixed off-by-one error in the message code values for the role request/reply messages.

Use Java properties (either via config file or command line) for per-module specific configuration files. Note: This obsoletes previous command line configuration properties apart from -cf (configuration file).

Fixed JUnit tests.