pseq: Create UCD90xDevice class

Create the UCD90xDevice class in the phosphor-power-sequencer
application.

This is a base class for the UCD90x family of power sequencer devices.

Tested:
* Performe

pseq: Create UCD90xDevice class

Create the UCD90xDevice class in the phosphor-power-sequencer
application.

This is a base class for the UCD90x family of power sequencer devices.

Tested:
* Performed the following tests on Rainier and Everest systems
* MFR_STATUS value obtained successfully
* Verified error paths and exceptions thrown

Change-Id: I430ffb95d96e228ce0245ae1c9cb63db72d590c5
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>

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