Move KeyValueStore to libchromeos

KeyValueStore is a key-value dictionary used to access and store settings
in a .conf file. It supports bool and strings only.

BUG=chromium:416932
TEST=FEATURES=test emerge-link libchromeos update_engine

Change-Id: I34a3add5536588ea1025976de659ad77ac6d8b39
Reviewed-on: https://chromium-review.googlesource.com/219552
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: David Pursell <dpursell@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
9 files changed