To do that, I've reorganized the code

Test: with ocaml 4.08, it is impossible to load the same function twice.
Hence the need to define p.mli files for graphs with several nodes.

Also, track missing files and the alea-coloring exemples.

Moved the python environment into 'tools', added Project object in the python environment alongside minor changes, created some scripts to test the environment, and changed make_dot function in topology.ml such that it removes the path of a file before using it as graph name.

The rationale is that
 - it is not always the cmxs that is necessary .e.g., rdbg uses .cma or .ml
 - it makes more sense to refer to the source code