Create inputmappers and accumulators directories

Inside the 'inputreader' directory, we create an 'mapper' directory
to hold the InputMappers and a 'mapper/accumulator' directory to
hold the Accumulators.

Bug: 140139676
Test: atest inputflinger_tests
Test: Touch, keyboard, trackpad, and mouse works on crosshatch
Change-Id: I4966919cd5b42353dd8c1e7cc7663f6c83765542
33 files changed