Fixed handling of SIPRegistrationDidFail and SIPSubscriptionDidFail exceptions

Ignore-this: 621aae78c578e355f83dce615ed357e2

darcs-hash:20100921125230-56b4d-21981b4abba2aa34465546af1b077367f99d630d
Fixed use of identity conditions

Ignore-this: 62eea5ad02b76f103b2ec79692a0fd92
    - Fixed schema
    - Identity elements can't be empty
    - Added FalseCondition extension in the AG Projects namespace
      It will allways evaluate to False
    - Add FalseCondition to a rule if no identity
      conditions are present (this may happen as a result for a
      an operation involving a contact or a policy

darcs-hash:20100920172725-56b4d-d6044673c7874a43e1fa46fa712953a330ebc856