Add chassis association to sensors

Add an association to the chassis for each sensor so that the Redfish
code can find them.  The forward association is 'chassis', and the
reverse association is 'all_sensors'.  This matches what other sensor
applications do and is documented in sensors-architecture.md in the docs
repository.

Tested: Checked the associations were present in the mapper and that the
sensors now show up on the sensors page in the web UI.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Iefb6d4dc2e5c9399d919e9e1b7c8dd04f20e7a3e
5 files changed