Language ID speed optimization

Reduced object creation for character unigram features.  Commented out
character bigram features (they add like 10 sec runtime to the 5s for
char unigram plus words).
Major speed improvements in language ID.

The language ID part on my test is down to 2.6-3s (from 13.7-14.9 in the
last version that used character bigrams).  Basically I made drastic
algorithm changes to avoid object creation.