[zen-12] Fixes based on functional testing
[zen-12] Fixes based on functional testing

- BaseForm should set $filter to the object's filter, instead of just returning
  it; ensures Form is using the same instance
- Typehint on ValidatorInterface in InputFilter factory, not Validator

marek-saji/zend-form,adamlundrigan/zend-form,adamlundrigan/zend-form,zendframework/zend-form,akrabat/zend-form,MadCat34/zend-form,akrabat/zend-form,zendframework/zend-form,MadCat34/zend-form,svycka/zend-form,svycka/zend-form,marek-saji/zend-form