Field widgets that use autocomplete should show a visual indication of invalid entry

Some of our fields (e.g. personField.tag) use autocomplete, but do so with an unintuitive UI pattern.

If you type in a fragment of text, but you don't select a choice, and you exit the field, the text fragment stays displayed. There should be:

1. a visual indication that this field is in an invalid state (e.g. turn it light red, or add an X)
2. any hidden value that is currently set should be cleared

For this ticket

• Fix this unintuitive pattern in personField.tag (you can see it in action when adding a relationship on the dashboard). Offer that up for review.
• If the fix had to be applied in personField.tag (instead of being done in a generic autocomplete javascript file) then also find all other core .tag files that do autocomplete, and have this unintuitive pattern, and fix them too.
• While you're looking at these different .tag files, consider whether there's a way to refactor such that they all share the same underlying implementation. (E.g. they could all delegate to an autocomplete.tag.)

(See TRUNK-2704 for an example of confusion caused by this.)