2) Don't allow to add new networks/implement existing ones for VPC in Disabled state. Disabled state indicates that there was unsuccessful attempt to remove the VPC, and the further cleanup will be taken care of by cleanup thread.
1) Added API frameworks for the feature. New commands:
* CreateVPCCmd
* ListVPCsCmd
* DeleteVPCCmd
* UpdateVPCCmd
* CreateVPCOfferingCmd
* UpdateVPCOfferingCmd
* DeleteVPCOfferingCmd
* ListVPCOfferingsCmd
2) New db tables:
* `cloud`.`vpc`
* `cloud`.`vpc_offerings`
* `cloud`.`vpc_offering_service_map`
and corresponding VO/Dao objects.
Added vpc_id field to `cloud.`networks` table - not null when network belongs to VPC
3) New Manager and Service interfaces- VpcManager/VpcService
4) Automatically create new VpcOffering (if doesn't exist) on system start
5) New Action events:
* VPC.CREATE
* VPC.UPDATE
* VPC.DELETE
* VPC.OFFERING.CREATE
* VPC.OFFERING.UPDATE
* VPC.OFFERING.DELETE