Update authentication for public release of gsasl 0.3.

Quick-n-dirty conversion to version 0.3 of the GNU SASL bindings.

Remove unnecessary TODOs

Implement converting stanzas to/from XML trees

Cleaned up the 'Component' module

Cleaned up the Client module, which opens streams in the jabber:client namespace.

Add some missing internal modules

Clean up a few internal modules, provide a smaller external interface to streams.

Use multiple stanza data types, with a common class.