CAS-1320 Refactor RADIUS authentication components.

Notable changes:
 - RadiusAuthenticator is created on every authentication attempt, which
   is required for some RADIUS protocols (e.g. EAP).
 - Close RadiusClient to prevent file handle leakage via open socket.
CAS-1320 Add unit tests.

Unit tests only verify component wiring at this point.
Specify network address as string to simplify Spring wiring.
CAS-1320 Use RadiusProtocol.name field for protocol name.
CAS-1320 Allow specification of TTLS inner protocol.
Merge pull request #304 from serac/jradius-new

CAS-1320 Refactor RADIUS authentication components.