[Why]
In some case, people may need x86 ABI version apk if they develop on x86 Android.
Support x86_64 ABI by default is better.
[How]
Add android::ndk::abiFilters property "x86_64".
Move `data/shaders` to `data/shaders/glsl`
Move `data/hlsl` to `data/shaders/hlsl`
Fix up shader paths in the cpp files to point to the new glsl location.
`data/shaders/hlsl/compile.py` still overwrites the glsl .spv files (for
now).
Issue: #723
