rework inputrc bindings

The inputrc file should not live in /usr/bin, so relocate it to
/usr/share/misc instead.

Let's also move our custom bindings out of the script and into a
dedicated inputrc file.  This makes the code a bit simpler and
easier to extend.

BUG=None
TEST=ran new crosh on a VM and tested key bindings still worked
CQ-DEPEND=CL:181282

Change-Id: I2bb2b911a1f2c92013f584b4706c4bcb39380fd1
Reviewed-on: https://chromium-review.googlesource.com/181281
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
4 files changed