Various validation improvements

Mainly to address http://www.fabrikar.com/forums/index.php?threads/ajax-validation-never-ending-in-forms.36907/ but other minor issues addressed also.

1. Move element validation to element.js in order to allow multiple element validations in parallel.
2. Clean code to minimise JsHint messages.
3. Remove ajaxmethod - post is default and since post must be used (since gets indicate a prefilter), this has no point.
4. Maximise use of mootools Request events to ensure clean use of spinner.
5. Correct typos in Fabrik Events (by adding corrected name rather than replacing existing)
6. Make consistent error reporting console log format.
7. Fix validation on db-join autocomplete.