Add packageconfig for dbus-sensors

Break up the dbus-sensors applications into packages so that users can
select which ones they want installed on their system.  The default is
to install everything.

This so that applications that will never provide sensor data for a
platform won't be installed and started.  A few of the reasons they
wouldn't be needed is:
* Not all systems contain the hardware that the applications access,
  such as the PCH or PECI interface.
* A system may use other applications for some of the functionality.
  For example phosphor-hwmon or phosphor-regulators may provide sensors
  for the power related hardware.

Packages can be removed by specifying them in a PACKAGECONFIG_remove
statement in a .bbappend in the appropriate layer.

(From meta-phosphor rev: 1e9ad9277f1829071c8474d0b2402b90a05d7e2b)

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I4422ce4b7abfb4be05d5617d543927132be70379
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>