- fix bug that custom angles were overwritten
- the norms only define screw heads, not the cut for them, so also a custom angle is possible to sink a metric screw
- use better step in UI since one changes the presets only in fractions of a millimeter (otherwise it would be a different hole size)
- handle case of no cut
- calculate change in diameter when adding depth to countersinks
- propose cut values also for UTS profiles
- the UTS defines coarse and fine while for ISO it is regular and fine, thus fix the name
- for the dialog: set minimum values to zero (angles etc. cannot be negative)
- initialization: thread direction only sensible if there is a thread
- initialization: hole diameter can only be changed if there is no profile
- initialization: only enable allowed hole cut parameters
- also for the ISO profiles it is allowed to countersink/bore deeper/less deep
- UI file: add some tooltips (the other changes were done automatically by Qt's designer)
