Drawj2d 0.6.4 released

This release improves Mavscript interoperability, supporting unicode characters (greek letters, etc) in labels.

Changes:
- new commands min, max
- command geom.vector enhanced
- commands label and texlabel enhanced:
escaped unicode chars (e.g. "escu00b7" for the unicode char U+00B7)
as internally used by mavscript-yacas
- svg metadata: creator set to Drawj2d