Attempting to add a little more detail around warning message for duplicate rule mappings

This really helps debug otherwise there's little context to pin-point the problem.
Add a little more context to the toString of injection result
Add InjectorConfig.toString and class this from InjectOtherRuleResult.toString
Make result private again
Remove some diffs
Merge pull request #10 from massiveinteractive/fix/improve-duplicate-rule-warning

Improve warning message around duplicate mapping