Support for euca-describe-*

[jeevanullas]

It would be really helpful if we can bring in support for following commands in the eucafrontend plugin

euca-describe-volumes verbose
euca-describe-snapshots verbose
euca-describe-keypairs
euca-describe-images
euca-describe-properties

[risaacson]

I just added these and more in a recent commit to the r2.2 branch.