Allow operator as a parameter for Advanced Filter in auto-complete Contact Reference field
Currently you can specify Advanced filters for auto-complete Contact Reference fields
EXAMPLE: To list Students in group 3: "action=get&group=3&contact_sub_type=Student"
But if I want to search all contacts with contact_sub_type != 'Student'
I propose that we pass operator something like contact_sub_type_op = 'neq'
which would do the same. This is consistent with what we are doing in reports as well.