Auto-ratio for scale in WCPS

[Dimitar Misev]

In scale() in WCPS we need to specify target extents of all coverage axes, e.g.

scale( cov, { Lat:"CRS:1"(0:767), Long:"CRS:1"(0:512) } )

It is annoying and error-prone to make sure that the ratio between Lat and Long in the original cov is preserved in the scaled one.

I propose to allow specifying the target extent for a subset of the axes: the extent for the remaining ones is automatically derived to preserve the ratio in cov.

E.g. for the example above

scale( cov, { Lat:"CRS:1"(0:767) } )

WCPS would automatically deduct that the Long axis should be Long:"CRS:1"(0:512).