[Myfaces Wiki] Update of "Drafts/Site/ExtVal" by BartKummel

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The "Drafts/Site/ExtVal" page has been changed by BartKummel.
The comment on this change is: Initial version.
http://wiki.apache.org/myfaces/Drafts/Site/ExtVal

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New page:
The Validator project was recently added under the MyFaces Extensions umbrella project. This project was created as a separate project by its lead developer under a different name, but joined the MyFaces project in December 2008. Although the full name of the project is MyFaces Extensions Validator, it is mostly referred to as ExtVal.

The goal of ExtVal is to eliminate the need to repeat validation code in the View layer of a Java EE application. This is often necessary in order to give user-friendly error messages. However, according to the Don't Repeat Yourself (DRY) principle, repeating code is not desirable. ExtVal can use several types of annotations in the Model layer of your application to generate JSF validations:
 * Bean Validation (JSR 303) annotations;
 * JPA annotations;
 * ExtVal annotations;

Thus, ExtVal eliminates the need to add validators to JSF pages as well as the need to repeat validation code.