fix(ngControl): unregister control from parent on detach

Un-register a control with its parent on detach, and also move register call to attach().
Right now, when a form element(such as an input) is removed from the dom,
the parent control does not remove it from the list of controls.

Closes #684
feat(forms): use the ng-form attribute as the name of the inner form

Closes #681
feat(NgModelValidator): provide support for min and max validations on number input fields
feat(NgModelValidator): perform number validations on range input elements

Closes #682