Disable LAZY explanation engine: it only works when a restart is achieved before calling explanations, so very specific usage (LNS only)
Explanations + log

- add some examples for explanations
- remove SILENT and LAZY from ExplanationFactory (first one is useless, second should be manipulated in a very specific context)
- add end-user explanation access
- light refactoring (remove pointless IDecisionJumper)
- add new logger in SMF
Merge branch 'feature-exp' into develop