Minor bug fixing + refactoring of UIAlertView related code

1 - remove self delegate from presentAlertWithTitle to avoid crash when alert is dismissed after streamer's dealloc
2 - removed direct usage of presentAlertWithTitle; now presentAlertWithTitle is only called thru failWithError;
3 - added missing code error for AS_FILE_STREAM_SET_PROPERTY_FAILED
4 - added isAborted method to represent the condition state==AS_STOPPING && stopReason==AS_STOPPING_ERROR
5 - added shouldDisplayAlertOnError flag to control alert display on failure