Support custom validation classes

[cristijora]

Bootstrap has validation states represented as classes which are pretty by default and can be customized really easy or which are overwritten in many front end templates such as admin templates or fancy css templates.

I wanted to support those states as well as custom validation classes rather than relying only on the error class.
Demo here
Usage:

formOptions: {
  validationErrorClass: "has-error",
  validationSuccessClass: "has-success"
}

Outcome:

Note: If you specify the 2 validation classes, they will overwrite the default error class.

[icebob]

Nice PR!