Creating and saving node groups

[adri326]

Like Blender's node editor, it'd be nice to be able to bundle nodes together to create a "node group", which would act like functions with inputs and outputs. Initial ideas for what features node groups should have are:

• Selecting a set of nodes and grouping them, removing them from the main node tree and hiding them within the node group
• Inputs and outputs for node groups, which interact with the nodes saved within the node group
• Panel/toggle to edit the nodes within a node group. Blender overlays the inner nodes on top of the other nodes for that, but having a separate panel for them is also reasonable
• Ability to rename the node group
• Ability to add/remove/rename inputs and outputs and ability to change the default color for these
• Ability to add/remove/rename settings, which would be mapped to colors (unsure about that one)
• Automatically create the inputs and outputs when creating the node group
• Ability to make several instances of a node group, making the workflow much faster
• Ability to save node groups to the library and to instance them from the library
• Preview of the result of the node group and its timing, like a normal node
• Differentiable decoration for the node, to tell them apart
• If a group node is selected and is opened in the group editor panel/overlay, then show that instance's preview and timings for each sub-node
• Node groups should be saved as individual files, to make it easier to share them with fellow TextureLab-ists!