Add low dose plans

[nbassler]

Low dose versions of plan 1 had lower energy layers removed due to lower limit for spot delivery. SOBP width was thus reduced, and plans needs to be recalculated for these cases.

[nbassler]

Check of weighting of low dose plans:

col 1: as in new RN files col 2: manual recalculation from original plan1 SOBP

Layer  0      0.0         0.0
Layer  1    0.384       0.384
Layer  2    0.501       0.501
Layer  3      0.6         0.6
Layer  4    0.677       0.677
Layer  5    0.741       0.741
Layer  6    0.794       0.794
Layer  7    0.839       0.839
Layer  8    0.879       0.879
Layer  9    0.914       0.913
Layer 10    0.945       0.945
Layer 11    0.974       0.974
Layer 12      1.0         1.0