Fix the response code for user credentials grant type

Fixes Issue #290
Fix credentials grant type test to assert that the response code for an invalid username and/or password is 401
fixes lack of namespaces in comments
adds Cassandra storage
Merge pull request #311 from bshaffer/add-cassandra-storage

adds Cassandra storage
Merge pull request #298 from adambutler/patch-1

Fix the response code for user credentials grant type
more information on skipped storage when applicable
Merge pull request #313 from bshaffer/more-information-on-skipped-storages

more information on skipped storage when applicable
Initial commit.
Move crypto token storage initializing to the server constructor.
Refactor getAccessTokenResponseType().
Add store_encrypted_token_string to the default config array.
Add createDefaultCryptoTokenStorage().
makes suggested improvements on @bojanz PR and adds tests
ensures that access_token storage is CryptoToken, even if defaults are set otherwise, using CryptoTokenInterface
Merge pull request #318 from bshaffer/bojanz-improve-crypto-token-dx

Bojanz improve crypto token dx
Support for client specific default scopes.
Updated PDO storage to support client specific default scope.
Added redis support and fixed sql statement in bootstrap file.
Moved client default scopes back into the clients table.