Replace rsync with python only alternative

[Akram9]

To make sync completely portable, it will be better to remove platform specific dependencies. A pure python implememtation will have no hindrance in being applied anywhere else.

[Akram9]

The rsync-alg.py added is more problematic than to get rsync working in itself elsewhere. Probably a different rsync python implementation is needed or rsync left by itself could do as well - at least for now.

While it works, it doesn't do the most required function - append the diff in the unpatched file.