pseq: Add power state/power good to Chassis class

Add the following to the power sequencer Chassis class:
* Power state and power good data members
* Methods to get power state and power good values

pseq: Add power state/power good to Chassis class

Add the following to the power sequencer Chassis class:
* Power state and power good data members
* Methods to get power state and power good values
* Method to set the power state to power the chassis on/off
* Method to monitor the chassis and update the power good value

Tested:
* Ran automated tests
* Tested new methods in simulation:
* Verified getPowerState() returned correct value when chassis on/off
* Verified canSetPowerState() returned correct values when chassis
on/off
* Verified setPowerState() set the power control GPIO correctly
* Verified getPowerGood() returned correct value when chassis on/off
* Verified monitor() obtained the current power good value when
chassis on/off
* Verified closeDevices() closed devices and released GPIOs

Change-Id: I1a8d404f9d1ebef651d4f5e7bf52e6375bbb158e
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>

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