Improve D-Pad Settings on Android

[DavidRGriswold]

Issue

At some point we should improve the Dpad setttings on Android. Right now, Axes and Buttons are mapped separately, which is weird and feels like duplication, plus if a controller reports both axes AND buttons, only the axis mappings are actually functional. Tested using dinput mode of an 8bitdo Micro - if I map ONLY the reported buttons and not the axes, the dPad does not work.

The ideal user-facing solution would be mapping Up, Down, Left, and Right separately, but have the program automatically detect whether the input is an axis or a button. if it's an axis, write something like "Axis 119 +" as the button code. If both are reported, prioritize the axis. This is how most emulators seem to do this. It could try to be smart and automatically map the reverse axis as well, so when the user maps Up it could automatically map Down to the reverse, to save the user a mapping.

Priority is low since the current setup does allow for all mappings, it's just not the cleanest.