* updated transform node (scale split into scale_x and scale_y, and added a repeat parameter)
* added blend modes (burn, dodge, lighten and darken)
* added a (very bad) blur node, based on generic convolution code
* rewrote normal_map node using convolution code
now load/save dialog use the non-editor classes (thus usable when running the project).
Refactored graphedit and node code (mainly load/save and adding and removing nodes).
Now the material node is aimed at Godot's SpatialMaterial. Textures are generated and passed to the SpatialMaterial (and not generated as shaders anymore).
Rendering textures requires a Timer (to wait for the viewport to be rendered). There has to be a better solution...
Added a couple more examples.
