Many changes!

New class: Model.

In this commit we added a Doxygen file and started documenting
classes: Experience and Model.

Incomplete refactoring of MDP based on changes due to new class Model.

Modified namespace and library name from MDPToolbox to AIToolbox.
Renaming of classes due to their contents.

In addition tested the code again, and produces the expected policy.
Updated README
Split MDP class in two parts: MDP and RLMDP.

In addition the Experience and MDP classes now support
again insertion of data through arbitrary container,
given they support operator[] and are of the correct sizes.

Source code for the both MDP and RLMDP needs to be correctly
written.

MDPSolver still needs refactoring.