Set limit pick and place area

[anhtuduong]

Set limit area for placing lego blocks to avoid singularity.

[anhtuduong]

Updated the limit in params:

'pick_limit': {
      'x': [0.0, 0.25286],
      'y': [0.39775, 0.78238],
},
'place_limit': {
      'x': [0.6, 0.94776],
      'y': [0.45482, 0.76],
}

Also implement a script in util that generate random position based on limit. Update the position accordingly in lego.world