Multi-group support for MotoPlus motion driver

See changelog in ted-miller/motoman branch.
This guarantees consistent structure alignment on all three supported robot controllers.  The three different compilers apply padding slightly differently.  During development, I found that at least one of these structs (don't remember which) behaved differently between the FS and DX.  So, I went through and ensured everyone of them is packed without any extra padding between struct members.