Allow specifying a separate runtime directory for managing multiple instances.

[Review issue 2452001]
Mail receiver works as all comm endpoints now.

[Review issue 2442002]
Merge branch 'master' of https://github.com/interactivespaces/interactivespaces
Email receiver now works like all other comm endpoints.

[Review issue ]
Blerg

[Review issue ]
Some cleanup of mail receiver.
Put proper Javadoc on mail receiver.

[Review issue ]
plugins-cache in run folder.
config folder settable from command line.

[Review issue 11482001]
Update merge from local master.