Refs #80 - Pass context values to constraints.
Refs #80 - Add BelongsToEntity constraint classes.
Refs #80 - Use setters instead of method args so as not be break backward compatibility.
Refs #80 - Simplify validation code.
Refs #80 - Remove arguments passed to getConstraints.
Refs #80 - Set the contextData in the validate method instead of in its own setter.
Refs #80 - Create separate class for validators that need context.
Refs #80 - Revert last commit.  Make the main class accept a data context and an optional entity context.
Merge pull request #80 from synapsestudios/feature/80-add-belongs-to-entity-validator-constraint

Add BelongsToEntity validator constraint