Added Authentication-method-specific sub-flow aware of and enforcing matching of Principal

Where a specific authentication method is required, CAS first requires the basic username-and-password login. The result of that basic login is CAS knows about an authenticated Principal.

Here's the punchline: sub-flows modeling particular authentication methods need to be aware of, reflect, and enforce that the additional authentication they are obtaining authenticates that same Principal.
Renamed test class to appropriately reflect the the behavior examined.
Merge pull request #32 from Unicon/FORCE-PRINCPAL-MATCH

Added Authentication-method-specific sub-flow aware of and enforcing mat...