Extract ModelPathSuggestionProvider to a separate class

+review REVIEW-5153
Don't bleed ModelRuleDescriptor to unbound rule reporting code.
Simplify using builder for UnboundRule.

+review REVIEW-5153
Simplify using builder for UnboundRuleInput.
Simplify UnboundRulesProcessor.

+review REVIEW-5153
Add tests for ModelPathSuggestionProvider

+review REVIEW-5153
Rename test class to match convention

+review REVIEW-5153
Fixed typo.
Add unit tests for UnboundRulesProcessor

+review REVIEW-5153
Merge branch 'master' of github.com:gradle/gradle
Change: Correct some misspelling and duplicate words
Merge branch 'master' of git://github.com/brewerc/gradle
Mention Clark Brewer as an contributor in release notes