Do not allow an alias to be deleted if its currently referenced ina  rule.
Do not allow an alias to be deleted if its currently referenced ina  rule.

Ticket #914

phil-davis/pfsense,ch1c4um/pfsense,NewEraCracker/pfsense,NOYB/pfsense,dennypage/pfsense,BlackstarGroup/pfsense,NOYB/pfsense,BlackstarGroup/pfsense,phil-davis/pfsense,BlackstarGroup/pfsense,ptorsten/pfsense,ch1c4um/pfsense,ptorsten/pfsense,dennypage/pfsense,NewEraCracker/pfsense,dennypage/pfsense,brunostein/pfsense,jxmx/pfsense,NewEraCracker/pfsense,brunostein/pfsense,jxmx/pfsense,brunostein/pfsense,jxmx/pfsense,phil-davis/pfsense,pfsense/pfsense,phil-davis/pfsense,pfsense/pfsense,dennypage/pfsense,ch1c4um/pfsense,pfsense/pfsense,pfsense/pfsense,NOYB/pfsense,BlackstarGroup/pfsense,NewEraCracker/pfsense,ch1c4um/pfsense,ptorsten/pfsense