Refactoring to use the C++-based UIO objects. The Liberio and Ethernet
objects now open the UIO before using it, and close it once done.
Reviewed-By: Martin Braun <martin.braun@ettus.com>
- Moved nijesdcore to cores/
- Moved udev, net, dtoverlay, uio to sys_utils/
- Made all imports non-relative (except in __init__.py files)
- Removed some unnecessary imports
- Reordered some imports for Python conventions
