support pattern validation

[dgrammatiko]

Pull Request for Issue # .

Summary of Changes

HTML5 NATIVE validation is done through pattern="something"
The validate.js is adjusted so if pattern tag exists will take precedence else we fall back to the rules

Testing Instructions

• try adding any of the patterns to a text, email, etc field and see if this works
• use http://html5pattern.com/Names for reference

Add pattern="[a-zA-Z]+" after https://github.com/joomla/40-backend-template/blob/master/administrator/components/com_content/models/forms/article.xml#L13
Create a new article and try to submit withou title and with title = (87587676) (or any other number)

TODO

• Add patterns to all the forms all over the admin area (form.xml)

Documentation Changes Required

[dgrammatiko]

Don't merge till joomla/joomla-cms#13094 is merged

[dgrammatiko]

joomla/joomla-cms#13094 is merged and this one is updated