Added support for Security Groups via a new extension.

- Added migrate changes for new database artifacts.
- Added models for Security Groups and Security Group Rules.
- Definition and addition of Controllers for API.
- Views for Security Groups and Security Group rules.
- Extended taskmanager to use newly created  Security Group on instance
  creation, and to clean it up on deletion if extension is enabled
- Added new flag to conf to enable "reddwarf_security_groups_support"
- Integration tests.

Implements blueprint: security-groups

Change-Id: I44053359c12e53a9e549bd334e628ecd249d8ba0