Noun phrase extraction, date restrictions, unit tests

Progress since February commit:

1. Eliminated the tree balance bug and a couple more bugs that were causing index
   errors. I have not re-run this on the GigaWord corpus but I'm guessing those were the 
   bugs that required trapping earlier

2. Implemented date restrictions

3. Implemented a new agents dictionary format: this is the first of the format changes
    that will modify these to the point where they are not compatible for TABARI 
	dictionaries
	
4. Program can pull out noun phrases which correspond to actors not in the dictionary: 
	this is controlled by the parameter new_actor_length in config.ini (see that file 
	for description of this feature)

The unit tests now have 128 records, so this is successfully passing most of the TABARI 
unit tests after these are modified so that they will actually parse (TABARI was working 
with simple pattern recognition a lot of the time, and many of the unit tests have 
required revision)