Split utils in multiple files
Add a signature feature

The idea is to be able to infer simple patterns from string data; for
example for telephone numbers.
Basic command line interface
Discrete model, using histograms

Possible improvement: the model-building phase should abort as soon as
the number of classes becomes too large
Add extra debug output to gaussian models
Fix dboost-stdin to use the new interface
Add floats to autoconv
Rename parsing to autoconv
Fix dboost-mimic2
Remove dead function in dboost.py
Fix: add a reset() method to models and call it after each table scan in mimic2
Minor fixes in dboost-stdin and dboost-mimic2
Add strings themselves as a feature, now that we have histograms

Plus a few TODOs