Extracting noid template to configurable

Prior to this commit, the template for NOID creation was hard-coded in
IdService. By extracting the template to a configuration option - with a
default - institutions can further customize what will very likely be
the a portion of the URL for their repository objects.
Merge pull request #114 from jeremyf/allow-easy-override-of-noid-template

Extracting noid template to configurable