Added new setting account.sip.enable_outbound_proxy

darcs-hash:20100219231956-58252-85856b5259207220cd4d597e5cd7ae1b767f7374
Simplified presence, xcap and dialog settings

darcs-hash:20100221151041-58252-9f9297fa8632513b026d3924de16dd1c49382b4f