Load jolokia properties from OSGi ConfigurationAdmin service

Hi Roland,

I was configuring the jolokia osgi agent, trying to get it to read properties from a config admin .cfg file with no success.  Pulled up the source and found a TODO for this feature.

I took a stab at adding this functionality, modified the current activator unit tests and added a couple tests for the config admin functionality.

Also verified working in my karaf 3.0.2 environment.

This is my first github pull request, so hoping that I'm doing this correctly!  

Please let me know what you think!

Thanks,
Ed