Reduce Fixation Points

If the toggle is switched to "On", the algorithm is allowed to reduce fixed displacements which aren't necessary to withstand the boundary conditions.

Therefore, fixed displacements need to be created as separate items.

If Reduce fixation points is deactivated, each fixation will be part of the new design.

If Reduce fixation points is activated, the optimisation algorithm is allowed to reduce them accordingly. At least one will stay and cannot be reduced.