EC2 VPC instance attribute security group modification - EUCA-9615

VPC instances now support modification of security group membership.

Messages / bindings are updated to match the current SOAP/Query APIs and
to cover all current attributes (messages should be correct but we do
not currently support all functionality)

EUCA-9615
Cloud initialization does not require hibernate cache - EUCA-9742

EUCA-9742
Merge remote-tracking branch 'origin/dev/sjones/EUCA-9742' into testing