Now source files handling is delegated to functions defined
in `sourcefs.c` file. By encapsulating methods for managing
the underlying source files structure we ensure that all
code changes to the source file protection strategy will be
localized to `sourcefs.c` file.
Also changed Makefile to use more sane way of handling
options and build flags.
After some consideration I decided to use C instead of C++ because:
* `libfuse` is written in C.
* C is simpler.
* My original concerns with using C turned out to be BS.
