App: Improve rerouting settings

[devemux86]

@linux-user

viaPoints - mandatory
shaping points - may be skipped

Rerouting now works as described by @SchlesiM in waypoint types topic:

@SchlesiM

rerouting should of course only omit all shaping-points before the next unvisited visit-point - not those behind it. Because a detour/rerouting should only affect the part of my route which leads to my next unvisited visit-point, not the whole route. This way the impact will remain as minimal as possible.