Rule tree initialization: Improved checks and error messages
Rule tree initialization: Improved checks and error messages

- Fail if rule couldn't be added to the rule tree (unless
  rule.optional_rule is set)
- error messages: print modename, too

OlegGirko/ldbox,ldbox/ldbox,OlegGirko/ldbox,h113331pp/scratchbox2,h113331pp/scratchbox2,h113331pp/scratchbox2,OlegGirko/ldbox,h113331pp/scratchbox2,ldbox/ldbox,ldbox/ldbox,h113331pp/scratchbox2,OlegGirko/ldbox,ldbox/ldbox,OlegGirko/ldbox,OlegGirko/ldbox,ldbox/ldbox,h113331pp/scratchbox2,ldbox/ldbox