Support axis-based input

[Nockm]

Left and right sticks

Should be floating, i.e. the centre jumps to where touch begins, then input is relative to that point on each touch move.

Triggers

Should be fixed, i.e. positions are absolute.

Directional pad

Should not be buttons, but should be a fixed-position stick whose analogue values are translated into one 8-way direction.

[Nockm]

All axis-based inputs are now supported.

There may be slight issues (e.g. floating stick extents should be a circle, not a square), but features look to work as intended.