Added a class for gradient (that handles serialization and shader generation), and updated the GradientEditor.
Added a "Types" class that handles values serialization.
Updated linked_control and config_control to link to GradientEditors.
Started adding the "remote" node, that can control important parameters of the graph and save/restore configurations of groups of parameters. This should help creating easily configurable materials.
Added new "mosaic" example
Exporting a material will now create a SpatialMaterial. The Material graph node
now generates different textures when used as a Godot addon (metallic, roughness
and ambient occlusion are merged into a single texture).
Rendering code (that was in graph_edit and node_base scenes) is now in a single "renderer scene" attached to the main window.