Add --security-group option to port-update

port-update --security_groups list=true ... is not user-friendly.

bug 1161078

This commit also changes the followings:
- Add --no-security-groups options to port-create for consistency.
- Make --security-group and --no-security-groups mutual-exclusive
  to prevent both options specified at the same time.

Change-Id: Ibfe165a0cbdfb0eb582784c80a3371de33108fdb
Handle host side SSL certificates validation

 - add --os-cacert option which allows to set a file containing
   certificates of root CAs (certificate authorities) that are
   required for validation of HTTPS servers SSL certificates

 - wrap httplib2 SSL certificates validation errors with a
   custom quantumclient exception

Blueprint: quantum-client-ssl

Change-Id: I4e6a7d177ba14314ba9bed613ec2684bffc35222
Merge "Add --security-group option to port-update"
Merge "Handle host side SSL certificates validation"