Combine AxisToAxis plugins

[spadino]

As per our Discord conversation, I suggest a kind of logical grouping for Axes. I propose a modifications to actual AxisToAxis plugin to be able to accept 1 to 3 input/output - linear, circular, spherical movements - so to avoid cluttering the select dropdown with three different plugins.

@Snoothy @evilC
It could be done implementing a dropdown control inside the plugin witch permits to choose between 1, 2 or 3 i/o, and an hook which reload the plugin with the current configuration.

[evilC]

I don't think it could be done like this without fairly major changes - how many inputs a plugin has is controlled by the source code of the plugin.
This is also potentially less efficient at run-time, as more checks need to be made etc.
Additionally, when moving from 1 to 2 to 3 axes, you may well want different DeadZone code etc (AxesToAxes has a circular dz).

[Snoothy]

Plugins have a specific amount of inputs and outputs at compile time, by design, and won't change any time soon