Updated with latest from FileIO

1) Updated with isMountPoint etc to FileIO.
2) Result is its own class
3) Added FileSystemWalker to the repo since it is very, very closely related.


*I did not add the unit tests.   I do think that is a good idea once we put these in a common place. 
It would be pretty easy to have a CMakeFiles.txt that just build all the source files and make one executable unit test. I.e. similar to the setup that I used for* [Concurrent<T>](https://github.com/KjellKod/concurrent/blob/master/CMakeLists.txt)