Also squashes:
[Sketcher] Create center of gravity constraint in planegcs
[Sketcher] typo
[Sketcher] Use accurate "weights" for knots
By weights we mean the linear combination factor B_i(x) such that
spline(x) = sum(pole_i * B_i(x)) for _non-rational_ splines.
[Sketcher] Use more appropriate weights for knots
These are relevant for knots _away_ from any ends (and possibly other high
multiplicity knots).
[Sketcher] Make COG constraint weights user-definable
[Sketcher] Make `flattenedknots` for periodic B-Splines
[Sketcher] Fix incorrect setup of `flattenedknots`
Without ensuring enough space, iterators become invalid. These iterators are
needed because for periodic B-splines we need to pad flattenedknots with offset
values within flattenedknots.
Apparently there is still some iterator issues even after the reserve. Just use
fresh vectors instead.
[Sketcher] Apply knot constraints by parameter
Hopefully this will allow directly applying constraints on knots.
[Sketcher] Disable some knot updating
[Sketcher] Use center of gravity constraint on knots
[Sketcher] Fix knot COG constraint for periodic splines
[Sketcher] Add start/end point of periodic spline to solver
This removes the trouble of transferring constraints to the underlying knot.
[Sketcher] Support knot constraints on rational B-splines
[Sketcher] Remove virtual from overridden methods in planegcs
Follow 0penbrain's comments
[Sketcher][planegcs] Use `unsigned int` in signatures
Also `size_t` at places
Suggestions by @abdullahtahiriyo
ba4f2bf128