Support for THR4 - on BBBBk

Playing with Beagle Bone Black again.
Readme updates on conversion - no using Debian

Now mounted on Lynxmotion Round Hex with 4DOF THex legs.

Also starting to merge so only one set of sources for main hexapods.

Note: the _fixed part is that this version is still using fixed point
math.  Will soon try Floating point
Right version of file