r.surf.fractal: Added seed option and -s flag to module

[Shashankss1205]

Here is my proposed solution to the issue raised #1044. I have written the code for adding seed and -s flag for reproducibility, along with a unit test for verifying it's functionality

[petrasovaa]

@Shashankss1205 do you plan to keep working on this? There is not that much missing (a simple test would suffice) and fixing the compilation error should be easy.