AXY:Blending

Blending Behavior:

1. global BF (<robot>.bf=<NUM>) is the default BF
2. local BF (move <robot> BF=<NUM>) overwrites that default per motion
3. this results in an effective BF per motion
4. global BFP initialized by the system to -1
5. local BFP overwrites global BFP per motion
6. this results in an effective BFP per motion
7. if the effective BFP is >= 0 (not negative), it overwrites the effective BF for the previous motion
8. the same shall apply to CP and CPP

with some side effects:

1. globally setting BFP to >= 0 is probably a bad idea, because it will

overwrite any and all elaborate local BF, but that's the spec.

See Also: Issue 2847