[bug report] Rebar spacing algorithm problem

[hippi-viking]

The custom rebar spacing algorithm does not work well in case one tries to leave a gap in a general rebar spacing and then continue on with the previous pattern. I think it might be becase at a change in the spacing pattern the previous rebar distance is also taken into account. (Note the algorithm - probably - works well if 2 or more bars are spaced out with the new distance - like in case of a column - but it does not work when only a single bar is spaced out differently from the others.)
So for the previous example: let's say we have 3 bars @ 200mm, then 400mm gap, and again 4 bars @ 200mm. In this case the custom spacing would be something like 3@200+1@600+1@-400+1@600+1@-400, which is clearly not correct nor very intuitive.

[luzpaz]

CC @amrit3701