Implemented SASL SCRAM-SHA-1 Authentication

RFC5802 http://tools.ietf.org/html/rfc5802

Support for SHA-1 but would be easy to support other hashing algorithms
in the future. Does not support channel binding.
Merge pull request #341 from ChatSecure/scram-sha1

Implemented SASL SCRAM-SHA-1 Authentication
XMPPMessageArchiving Default Log Level