Added Image node that can be used to import textures Renamed all get_shader_code methods to _get_shader code so a caching system can be integrated in node_base (and we can get rid of get_source_rgb and get_source_f functions)
Also create a copy of materials and shaders when the addon is started so it does not change the addon's default materials.
Also started replacing LineEdits with Spinboxes
- updated all nodes (load/save support and shader generation) - added warp node
