update Storage/Pdo

change JWT fetch to fetchColumn for getClientKey method to fix key validation issue.
Add support for non-expiring refresh tokens.
Add docs to storage.
Merge pull request #335 from bojanz/refresh-tokens

Add support for non-expiring refresh tokens
Merge pull request #333 from lgelfan/develop

update Storage/Pdo
fixes #341 - additional test cases for user credentials with public clients
Merge branch 'develop' of https://github.com/bshaffer/oauth2-server-php into openid_connect
OPENID-CONNECT - fixes old tests, adds tests and makes them pass, moves UserClaims into OpenID dir