first changes after fork:
* eliminated bidirectional dependency between Filter and Command classes
* allow RelyingPartyRealm to be used in configuration, not just the misspelled ReylingPartRealm
* allow session attribute storage as an alternative to cookie storage; cookies are still the default
* Split code out to new classes to control things like Assertion serialization and deflation.
* Moved StatelessFilterCommand to ACSFilterCommand which now stores state around request so that the same objects don't have to be passed along to each and every method.
* Allow cookie persistence to apply to all subdomains of the configured relying party URL. Will make this a configurable option in a later commit.
* Made vert location not have a leading slash, which was making the path look at the root of the system and not the root of the project as previously intended.