New monitoring system with enviromental vars

Ok I really need help here. Ref: https://github.com/lisa-lab/pylearn2/pull/1070/files

Anyway I added the configuration system of Theano. I'll propose them a pull request to generalize it. In configparser there is "SemicolonParam", which is a class that in the future should check the format of the parameter (which is a semicolon separated param).

What do you think so far?

Example of use:

    PYLEARN2_FLAGS='channels_include=train*' python ../../pylearn2/pylearn2/scripts/train.py NN_static2.yaml
I'll merge any PR to Theano with that fix. No test needed, I don't see how this can be easily tested inside Theano. Pylearn2 will test it.