doc'ed Computer Device.

- partial doc of devices.rst and classes ref'ed from it, not done yet.
doc'ed devices.rst and classes refernced from it

-classes doc'ed:
Device
Device Event
doc update and trim down of Display dev.

- added docs for Computer, Display, and Experiment devices.
- Also made about 1/3 of Display device methods private as they would
serve no end user any purpose.
- added back the page listing existing device support for each OS, and
the planned device list for 2013.
Merge branch 'master' of https://github.com/isolver/ioHub into new_docs
Computer class doc rewrites