add ctnr field to cydns objects
fix recursive import and field name conflict
migrate CNAMEs with containers
add containers to MX during migration
add ctnr to AR and PTR during migrations
remove custom PTR.filter_by_ctnr
give nameservers a dummy container
refactor ctnr retrieval logic
fix schedule_zone_rebuild race condition
remove label-domain stuff from PTRs
re-add created and modified fields to PTRs
resolve id field conflict
add ctnr field to PTR model
fix ctnr_from_zone_name actually uses names
Merge branch 'add_containers_dns' into dev
Merge branch 'ptr_revert_labeldomain' into dev

Conflicts:
	cyder/cydns/ptr/models.py
fix fields for ptr creation during migration
add views to PTR objects
fix zone migration format for static interfaces
various form and mixin fixes for PTRs