JCLOUDS-602 - Add support for volumeType, iops and encrypted to EC2 volumes

Note - still missing adding these to the createVolume* methods, but
that's going to involve a non-trivial change to something like
CreateVolumeOptions.class rather than the current simple arguments.
Actually, I should probably change it all to primitive - I was going with non-primitive for places where it's optional, but I think it actually shows up in every EBS volume query now.