Coordinates must work with unitless lenghts

[Johannes T]

Coordinates now only work with lenght objects that must have a unit. However, paths work with unitless coordinates. Therefore, it should be possible to initialize a coordinate from two floating point number. In this case, initializing a (or two) coord.Len objects can be completely avoided.

However, care must be taken not to mix unitless lengths and coord.Len objects.

[Johannes T (jo-ey)]

coord.Len objects must be initialized with a unit now. coord.Point objects can now be initialized either from coord.Len objects (with unit) or from unitless numbers (floats). Care is taken not to mix lenghts with and without units in single object specifications.