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
Is the issue that you need to override fetch_val_for_key2 in pylearn2?
Maybe Theano should be modified to make fetch_val_for_key2 a method of ConfigParam. Then in Pylearn2 you could subclass TypedParam and override fetch_val_for_key2, but not copy any of the rest of the implementation.