Fix problems in grammar

- Two elements had same name
- Additionally commong_tag relied on two optional strings, instead
of shared element named_elem
- constr_param should take id of a property and not the property
definition itself
Add std DOMMLite model

- Adds model that will be reused throughout the application. This model
provides basic DataTypes, Tags and Validators for new models to reuse
Add clean before every build to avoid errors