moving phosphor-host-ipmid: entity config to json

[Patrick Venture]

Currently the entity-configuration is in yaml and compiled in.  We're
the only ones using this downstream, as far as I can tell.  I'd like
to move it to json and make it part of the phosphor-ipmi-config
bucket.

This entity config:
https://github.com/openbmc/meta-phosphor/blob/master/recipes-phosphor/ipmi/phosphor-ipmi-host_git.bb#L106

Used:
https://github.com/openbmc/phosphor-host-ipmid/blob/f442e119aed2dc87f320bf230ad39e7dc5c72524/sensorhandler.cpp#L29

The format will be similar.

Any objections?  We're working on bringing up a system where things
will need to be determined at run-time and new json files spat out --
basically.  And this will be one of those files.

Patrick