Serialize/deserialize support in BaseParser

[juditacs]

• dump_to_file: dumps the list of parse_all method's yield values to file in cPickle format
• load_from_file: reads cPickle file
• parse_all: yield language data, one dictionary/language. The subclasses must override this method in order to use the serialization
• parse_or_load : if the pickle file exists, load it instead of parsing. If it doesn't exist, parse everything and save it in pickle

Discussion is welcome