Stormpath.* properties should take precedence over config in shiro.ini

[bdemers]

This is tricky due to how Shiro loads an object graph from the shiro.ini, but from a user perspective, the current behavior is less obvious.

Currently if a user has a shiro.ini that looks like:

[main]
...
stormpathRealm.applicationHref = http://etc..

Then there is NO way of overriding this via the command line using an environment variable of STORMPATH_APPLICATION_HREF or -Dstormpath.application.href=...

This is slightly related to SHIRO-501 (using system properties in the shiro.ini, but not exactly the same.