Adding set_region and list_instances methods to RackspaceCtrl class.

Adding tests for set_region.
Adding methods to list, get, and delete instances.
Re-working instance related methods to maintain a local list.  Will re-add
this functionality if latency impacts user experience.
Adding set_region and list_instances methods to RackspaceCtrl class.

Adding tests for set_region.
Adding methods to list, get, and delete instances.
Adding methods to create, list, and delete key pairs.
Merge branch 'gns-25-26-27-key-pairs' into gns-21-22-23-24-instances

Conflicts:
	gns3/cloud/base_cloud_ctrl.py
	tests/test_cloud_integration.py
Adding create_instance method.
Adding methods to base_cloud_ctrl:
  create_instance, list_instances, delete_instance, get_instance,
  create_key_pair, list_key_pairs, delete_key_pair

Adding exception classes
Re-working exception handling to reduce code duplication, ease base controller
class abstraction.

Adding additional exceptions.

Adding unit tests for exceptions based on API response HTTP status code.
Adding tests to test_cloud_integration.py

Cleaning up comments, etc before pull request
Removing whitespace.
Merge branch 'dev' of https://github.com/planctechnologies/gns3-gui into gns-21-through-27

Conflicts:
	tests/test_cloud_integration.py
Merge branch 'dev' into gns-21-through-27
Merge branch 'gns-21-through-27' of https://github.com/planctechnologies/gns3-gui into gns-21-through-27
Fixing tests
Merge pull request #8 from planctechnologies/gns-21-through-27

Cloud API calls - GNS-21 through GNS-27