pattern.metrics tpdf()

Probability density function for the Student's t-distribution.
better module caching for _multilingual()
better relative imports
pattern.en parser improvements

- tokenizer handles paragraph linebreaks (titles may not have an ending period, must be inferred from whitespace)
- tagger recognizes numbers (CD) by default
expanded tagger lexicons (better handles for quotes and apostrophes)
expanded sentiment lexicons
small fix for French verb lexicon
small fixes for French tagger (better handling of apostrophes)
some more comments
pattern.fr unit tests