Add Push interface for creating macros

[brunchboy]

It would be nice to be able to create cue macros on the push by pressing the Duplicate button, which would go into an overlay that let you select running cue-based effects and which would light only the free grid pads; as soon as you touched one of those, the selected effects would be saved as a macro on it. You could cancel by pressing Duplicate again (or perhaps by hitting a grid cell with no effects selected). The available grid pads should only be dimly lit until at least one effect is selected. Naming would just be “Macro P1” and so on because there is no keyboard.