Add asMap, asSingleValuedMap, asMultiValuedMap, and asMultimap methods to convert a Set of ConstraintViolation into a JDK or Guava Multimap. Overloads provide the ability to customize the translation from a property Path to the map key.
Add pathStringOf, a pure convenience method to eliminate boilerplate.
Clean up a few minor grammatical errors in javadoc.
Closes #1169 Closes #1170