Added sphinx documentation.
Moved latex notes to different directory

To be able to embed them in the documentation I moved the latex notes to a subdirectory of the documentation directory and added a Makefile.
Ignore files in _build subdirectory and files produced by latexmk
Moved main part of driver into if(__name__ == '__main__') block.

This is required by sphinx.
Added missing tabstops

tabstops were not formatted correctly before, this commit fixes this.
Updated documentation, automatically compile latex notes

Wrote an introductory paragraph for the documentation, added target for automatically compiling the latex notes and copying them to the build directory.
Updated documentation and cosmetic code changes.
Fixed two bugs.

The solveApprox() method has been replaced by the solve() method everywhere. The multigrid class does not have any parameter tolerance.