refactored rules out of lexicon and into lexiconfn for easier transition to new lexicon
features whose value are either :top or false are considered as uninteresting.
+ ‘leggere’
add intransitive sense of “leggere”
handle cases where (get-string) does not return a string as it should.
make sure (get-in word [:italiano]) is a string before trying string-type operations on it to avoid exceptions