CAS-1365: Access rules to the management webapp are externalized.

Instead of having adopters tweak the xml file, by default an external file is provided
that can list the user accounts who may have access to the webapp. This appears to
moderately address use cases better in cases where ldap or jdbc backends are not
available or may not be at all needed.

https://issues.jasig.org/browse/CAS-1365
Merge pull request #334 from Unicon/CAS-1365

CAS-1365: Access rules to the management webapp are externalized.