Added functionality to Config to allow overriding local.conf with a spec...

...ified conf file

The system property name is: local.conf.override and can be found in the Config object as a constant. It is the pointer to where the overriden file is to be found. It can be an absolute or relative path.
maybe consider doing this on two lines, I don't think we should use something so complicated in a string insert
i.e. put the thing into a val, and then use it