Add ability to disable HVAC and steering wheel pages

Add ability to disable HVAC and steering wheel pages

Add configuration file options to disable the HVAC and steering
wheel pages.  Also includes a bit of refactoring around the
KUKSA.val databroker client mostly focused on cleaning up naming
for now.  If significant development continues on this application
the KuksaClient class should be used as the place where more
refactoring occurs.

Bug-AGL: SPEC-5142

Change-Id: I986c7cac4e6543e2a1ad40ebf436fd40e2ae2300
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
(cherry picked from commit 6b21032fc91b679353a53073f5570a25a4fd0991)