Support Mercurial VCS for version and release plugins

[kercheval]

Mercurial is a great distributed VCS with a natural syntax. Supported well by bitbucket.

http://mercurial.selenic.com/

[kercheval]

Possible java library for use of Mercurial

https://bitbucket.org/aragost/javahg

[kercheval]

Currently being worked on in the mercurial branch. Mercurial specific code has been removed from master since mercurial work is being done on a lower priority basis.