Create a Python submodule for MVA libraries.
Add basic utility functions to mvalib
Add half-done prepare lib.
Update prepare lib to a working version.
Add iter_entrylist() to utils.
Document utils.py
Update mvalib.prepare to the new spec.
Merge branch 'mva' into mva-lib
Rewrite the mvalib.prepare and base it off a class.

The interface has to be more flexible due to new requirements (using completely
different samples for training and testing). Replace the function with a class,
that can be used to set up and execute the preparation of training samples.
Merge branch 'mva' into mva-lib
Add MVA2 to $PYTHONPATH

Also move all Python files from the MVA2 directory to a subdirectory
MVA2/MVA2, so that they would not be directly importable. Since scripts
import them as if they are in a module MVA2, then with the new $PYTHONPATH
this is still possible.
Update the example/prepare script to the new API.
Update the samples in examples/01_prepare
Fix the storing of fractions to meta in mvalib.prepare
Create a training mvalib.train API.

Also update the examples/02_train.py example so that it would use
this new API.