Added PatternCoordinator class which returns a set of coordinated pattern generators

A PatternCoordinator is a set of coordinated pattern generators.
The pattern generators are named according to the labels parameter.
The dimensions to be returned are specified with the dims parameter.
PatternGenerators are first instantiated with the parameters specified in input_parameters, and then subclasses of ValueCoordinator are applied to modify the properties of these generators.
Attributes that you don't want the user to mess with, like metafeature_params, should not be mentioned by name in docstrings.  You can talk about what happens, but you would only mention the name if you want people to read from it or write to it.  I guess that means that it should be renamed starting with an underscore to emphasize that people shouldn't mess with it.  Plus we aren't discussing metafeatures anymore anyway, so it would be something like _feature_params or maybe _extra_keywords.  I can't quite remember what this is used for, so I can't say what the right name would be...