This adds a new Gpio helper class, which uses libgpiod under the
hood instead of the deprecated sysfs GPIO access. This class provides
the ability to get/set a specific GPIO, which is looked up by name.
Pull some general functionality out of a specific test case and create
a TestBase class. Future test cases will inherit from TestBase and have
access to this general functionality.
Add unit testing framework to MPM which can be run by calling
"make test". The testing is done using the built in unittest Python
module. Tests can be run on a dev machine or on the USRP itself when
compiling natively.
