Move infill_every_layers infill_only_where_needed into their own "Reducing Printing Time" section
New Quality section in GUI
New options: start_perimeters_at_concave_points start_perimeters_at_non_overhang
New option for disabling thin wall detection
New option to disable overhang flow
Move spiral_vase to vertical shells section
Add --gui argument to Build.PL
Update t/perimeters.t
Lower case option group titles
Rename adjust_overhang_flow to overhangs
Only work on GUI modules when --gui is supplied to Build.PL
Merge branch 'master' into xs