Block TSR library's place and place_on should be renamed.

[gilwoolee]

While reviewing for personalrobotics/magi#2, I realized that block tsr library has 'place' and 'place_on' tsrs, and it's 'place_on' serves as 'place' in many other object tsrs. For consistency across tsrs (so that same tsr name can be used for motion planning across multiple objects), 'place' should be changed to something like 'place_at' and 'place_on' should be changed to 'place'.

[vinitha910]

I renamed 'place' to 'place_at' and 'place_on' to 'place'. The changes are in block.py in the feature/MoveUntilTouch branch