JSF: Add an hint for duplicate attributes on faces tags

[NicolaIsotta]

• add a new duplicate attribute hint to existing ComponentUsagesChecker class
• minor refactors/optimization to the class
• add tests

The reason:

• duplicated attributes are runtime errors (facelets files are parsed with SAX)
• declared attributes are already checked so the new hint was pretty cheap

Screenshot:

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[mbien]

looks good to me.

You think this is something for NB 32? If yes please add the milestone. It would have to get in before freeze.

[NicolaIsotta]

Yeah, I think this can go in safely. I'll merge later unless there are objections.