Add Independent and Simultaneous motion group instructions

[kobbled]

Independent motion

linear_move.to(p1).at(100, 'mm/s').term(100).independent(group(1))
joint_move.to(p1).at(100, '%').term(50).independent(group(3))
Independent GP
GP1 L P[1] 50mm/s CNT100
GP3 J P[1] 100% CNT50

simultaneous motion

linear_move.to(p1).at(90, 'mm/s').term(100).simultaneous(group(1))
joint_move.to(p1).at(100, '%').term(50).simultaneous(group(3))
Simultaneous GP
GP1 L P[1] 90mm/s CNT100
GP3 J P[1] 100% CNT50