Add config file support to compass sample

The compass parameters like serial port name and sensor min/max values
are now stored in a .config file.  The base filename for the config
file is based on the USER environment variable.  For me the filename
ends up being adamgreen.config.  The adamgreen.config file in this
commit is an example of the supported settings.
Add config file support to orientation sample

Pulled config file support from compass into orientation sensor as
well.