Add Hibernate LengthValidator class
Move JSR303ValidatorFactory to better package
Add LengthValidator test for HibernateValidatorFactory
Add tests for Hibernate LengthValidator
Add new setValidators method without optional classes

Simplifies code because there is no need to add empty OptionalTypes.get()
call.
Add possibility to add multiple ValidatorFactories to ModelFactoryBuilder
Modularize JMobster

Smaller modules allow developers to only take the parts they need. Smaller
modules also help keeping the architecture better since it restricts
bad dependencies (e.g. circular dependencies).
Fix bug in indentation of backbone models

Simplified tests by removing unnecessary line changes. Those line
changes only made the tests hard to read since line changes in mocks
couldn't have the accurate enough indentation logic without being
too complicated.