Resolve "Transition to Low-level Fuse"

This Merge Request represents the first step to transition openio-fuse to use the low-level Fuse interface. The functionality has not yet been transferred. This will be done in issue #4 (closed). A number of improvements have been made in addition:

1. Modernized CMake with separate modules which also speed up compile time. Please ignore Warning when calling CMake. It's a bug, resolved in version 3.11 (see https://gitlab.kitware.com/cmake/cmake/merge_requests/1242)
2. Skeletons have been added for future functionality. Refer to separate backend classes.
3. Generally improved directory hierarchy.
4. Separate logging instances for modules.
5. Intercept library skeleton has been added.
6. Path utilities added.

Closes #2 (closed)

Dependency of #4 (closed)