implement IProjectionSpace

[gregsn]

https://github.com/vvvv/vvvv/commit/3875b7079204d106cc0a822a2ff3bb32562620fb#diff-dc9dac49f758a8824170070e3b0ef204

to get a pixel position posPix into projection space following steps have to be taken:

• identify the viewport the posPix is in
• get from window pixel space to viewport pixels: by just substracting left/top of viewport from posPix
• get from pixels to normalized viewport coords (-1/1 being lefttop 1/-1 rightbottom)
• undo the crop to get into normalized projection space
• undo the aspect ratio to get into projection space

this will help people to interact with their scene no matter how complex the setup

[gregsn]

the feature to see here is that the rendered cursor (the quad) is at the right place and is quadratic.

so this is my try of implementing IProjectionSpace:
gregsn@225100c
i had to do several other things to be able to use the newest plugin interface.
todo:

• make Preserve Aspect of WithinProjection true by default and add that change to the diffff.xml
• when rendering resuse the the FViewports instead of recomputing them