primstar 0.9.17-git

The Export LSL script has been rewritten with some functionality moved into a new primitives.py to act as a base for other export options.

There are improvements to Image - Import as Sculptie to support joined meshes and normal rotated sculpties.

There's a lot of little tweaks and adjustments including a more forceful screen redraw for Macs to hopefully fix the problem of the GUI widgets going blank after using the file selector. Packed images should now export correctly as png files.

Please report any new or continuing problems as we are (mostly) just bug fixes away from a 1.0.0 release now. The only planned changes are a little bit of extra LSL to make the builder look pretty