Implemented advanced log in CRFSlotFiller inference

[ClemDoum]

Description: Implemented advanced debugging logs for the CRFSlotFiller.

Until now debugging the CRFSlotFiller decisions was pretty obscure unless you put breakpoints in the code and used some pretty advanced tricks.

I added a log activated in debug level which prints token per token:

• The incoming transitions weights (to the current token label)
• The outgoing transitions weights (from the current token label)
• The token feature weights
• The list of feature extracted from the tokens but which are not in the CRFSlotFiller state features (likely not seen at train time)

[codecov-io]

Codecov Report

Merging #776 into develop will increase coverage by <.01%. The diff coverage is 93.33%.

@@             Coverage Diff             @@
##           develop     #776      +/-   ##
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+ Coverage    88.08%   88.08%   +<.01%     
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  Files           76       76              
  Lines         4497     4540      +43     
  Branches       855      870      +15     
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+ Hits          3961     3999      +38     
- Misses         401      403       +2     
- Partials       135      138       +3