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.
I'm going to leave Iops as a non-primitive everywhere, because it's possible (though I don't think likely) that it could have a 0 value. I'm going to move encrypted to a primitive where it makes sense - i.e., in BlockDeviceMapping, deleteOnTermination is a non-primitive already, so I'll stick witht he same thing there.