not yet clean, need to see if pack/unpackRawdata are needed for server and myFig-client

need to unify message format:

STATUS/RECEIPT/SIGNAL: 'HEADER-fix-size MSG-fix-size STATUS-fix-size'
INSTRUCTIONS/DATA:     'HEADER-fix-size MSG-fix-size CONTENT-var-size'

the fixed size are configurable. if user need longer msg he can overwrite
class with constants.

The default pack/unpack of myAxes are just eval of
the string. Can be overloaded by user.