Target name refactoring

[Andrew Geissler]

Some design decisions came out of my last set of changes in the
OpenBMC state area.  There was a proposal to rename our targets
responsible for booting and powering on/off the system.

Currently we have this:
- PowerOn: obmc-power-chassis-on.target    obmc-chassis-start.target
- PowerOff: obmc-power-chassis-off.target    obmc-chassis-stop.target
  obmc-stop-host.target

The obmc-power-chassis-*.targets are responsible for doing whatever is
required to apply pgood to the chassis.
The obmc-chassis-*.targets are responsible for starting and stopping
all host related services
The obmc-stop-host.target is where we have the soft power off service
(notify host of shutdown, wait for host to shutdown gracefully)

Refactoring Proposal:
- First the chassis-start and chassis-stop target names don’t make
sense anymore with the new bmc, chassis, and host state break down’s
so:
  - Rename obmc-chassis-start.target to obmc-start-host.target
  - Rename obmc-chassis-stop.target to obmc-stop-host.target
  - Rename the current obmc-stop-host.target to obmc-shutdown-host.target

The target relationships are then the following:

obmc-host-start.target requires obmc-power-chassis-on.target
obmc-shutdown-host.target requires obmc-stop-host.target requires
obmc-power-chassis-off.target

When a system goes to the quiesce target, the host state manager will
call the obmc-stop-host.target.  Otherwise, the host state service
will call the obmc-shutdown-host.target when power off is requested.

Thoughts/Comments?
Andrew