Allow patcher contents to be turned into a "sub patch"

[HSJIII]

This idea is based on how synthmaker lets you group select items and turn them into a component, but it also includes some ideas which are tailored to patcher, itself. After you get all the work done of constructing a good patch, sometimes you notice that a section of your schematic should be a patch of its own... but it's too late to do that, because it's already very elaborate. The only way to make a "sub patch" is to go through and delete everything except for what you want to save as the sub patch... and now you can load that as a patcher preset. Although that's "okay", it would be best if one could simply group select the desired components and right click them, and select "create subpatch", which would make a new internal patch, complete with its own surface, etc (perhaps with its own surface tab up top on the patcher window)... then you could name it and (this part is critical) have a chance _save_ this new custom patcher to the patcher presets list, so it's accessible to other projects. Inputs to internal components with connectors leading out would be inputs for the subpatch... respectively the same with connectors leading out...the would become the patches outputs. This would require that patcher itself become able to receive and transmit a signal data type (red connectors) for primary ins and outs, which would be an infrastructure change, but it would be well worth it because of the added modularity.

If you do this, you might want to ask the user whether they want a surface control generated for each of the new patch's inputs (or give them a checklist of which ones to turn into surface controls). That's because when a user reuses this, they might plan to give it inputs from a surface or inside a patch, and you really can't heuristically intuit which one they have in mind.

[MCMorrise]

+1. It would indeed be very nice to bundle inst...