fixed bug in fs node getName

The return type of filesystem::Node's getPath function was a const reference to
an std::string, but the function actually returned a temporary value. Somehow
this dropped through the error checking mechanism of gcc AND clang. Now fixed.
fixed all -Wall bugs

Fixed all warnings the compiler started to emit when I added the -Wall flag to
the compilation command. The build should now be clean, making it easier to
spot actual errors.