Reworked Smack initialization

Move extension relevant configuration options from SmackConfiguration to
the extension. Introduced disabledSmackClasses that can be configured
via a system property or configuration file.
Send request after the PacketCollector was setup

This bug was introduced with 7bd7b3d24. Thanks to Lars Noschinski for
discovering it.
Properly escape PubSub item's text (SMACK-546)
Make JUL Loggers final (SMACK-536)
Add automatically scheduled pings in PingManager

replaces keep-alive functionality. SMACK-537
Remove non-SASL authentication code (SMACK-446)
Created 'tcp' subproject for TCPConnection

Renamed XMPPConnection to TCPConnection, since the other connection type
is also called BOSHConnection.
PingManager should notify PingFailedListeners only once

Fixes SMACK-548
Use correct namespace for MUC.getAdmins()

Fixes (again) SMACK-371