USB interface library that can bind and unbind devices in the heirarchy.
Implementation of some very basic unit tests for digital outputs.

The reverse test doesn't work and needs to be fixed.  It is marked pending currently.

Some minor changes to the library to support asynchronous tests and the removal of I/O watchers.
Remove the option to include a path to C .so modules in the Lua tests.
Include a binary version of the linux input header wrappers that are built as part of L000-515.