Added measures to avoid memory leaks. An instance of ModelObjectWrapper is a one-shot object, method close() must be called at the end of its life.

Some cleanup and organization of API.
More code cleanup.
Syntatic sugar for model descriptions.

Added simple model description with a single function set.

Support for deep copy for model description.
Renamed the main fitting class from fitter to Imfit.
Added support for creating model images (before and after fitting).
Added synthetic PSF image generators (gaussian and moffat).