Add 'angle' value to pen config and enable it to be used for PFM 'angle' value.

[led]

When using CMYK(& -extended) Colour Separation and certain PFMs that have an angle setting (eg Hatch Sawtooth), it would be nice to be able to optionally tie the angle to that defined for each pen, eg Y=0°, C=15°, M=45°, K=75°

It is of course possible to just spit out different per-pen versions at angles and then selectively combine them, but adding the above option would greatly simplify things.