JavaScript Validation should trim values and set focus on invalid field

[batmoo]

If invalid fields are found after validation, focus should be placed on the first invalid field. Field values should be trimmed to check for truly empty values.

Also worth noting, the (mostly same) validateForm is located in both common.js and wpAjax.js.

Patch removes redundant validateForm from common.dev.js and uses the one in wp-ajax-response.js (though, in retrospect, it may be better to move it to a more agnostic place so that non-ajax submits can make use of it too).

Patch trims field values and sets focus on the first invalid field.

common will probably be enqueued in more places than wp-ajax-response. I imagine it may have been intentional for both to exist.

As far as I can tell, the only place that validateForm is in use is on tags.dev.js. Even then, it's redundant as almost all of the JS validation on the site is being handled by wp-ajax-response.

Regardless, new patch restores validateForm on common.dev.js, adds trim and focusing, and I've added some indentation to the functions to make them a bit more readable :)