No perimeters on bridge area

This option is here to help slicing objects that have a counter-bore hole.

There are multiple options to resolve this problem:

• Remove perimeters : just relocate the perimeter from the bridge area.
  Pro (+): simple and effective.
  Con (-): some bridges aren't anchored on the both sides.
  

• Fill the voids with bridges: relocate the perimeter and extends the bridge area to fill the empty space. It will create an "hymen" that the user have to remove manually. Note that you can do that manually by creating a new cylinder at this position (right-clic on your part -> add part -> cylinder, in the right area unlock scales and change the X&Y size ; push enter and then move it into your hole ; change his z size to your layer height and enter the Z position).
  Pro (+): best counter-bore effect.
  Con (-): counter-bore cones with steep angle will destroy your piece from over-extrusion (even more than normal).
  

• Keep bridges: don't print any area that isn't a bridge. Too experimental, please don't use it until it improves a bit. Pro (+): ? simple?
  Con (-): will destroy your overhangs and I don't think it will print the counter-bore hole better either.
  

• Keep bridges and overhangs: It print the bridge like the previous option, but will fill the rest with a perimeter and "bad bridges". Very experimental. Pro (+): will push the right amount of plastic, like "Remove perimeters" but with less "one-side anchored bridges"
  Con (-): difficult to print.