Refactoring FAFT keypress code and adding usbkm232 interface.

Cleaned up code to breakout keyboard handlers into thier own classes.
And added support to send keystrokes via usbkm232 cable, which is
required for devices that do not have an internal keyboard.
BUG=None
TEST=Manual testing at desk

Change-Id: Iae13632447695e16e1fa1ce7d29deb41dc48a7fb
Reviewed-on: https://chromium-review.googlesource.com/182539
Reviewed-by: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Yusuf Mohsinally <mohsinally@chromium.org>
Commit-Queue: Yusuf Mohsinally <mohsinally@chromium.org>
5 files changed