tidying up, tooltips, l10n

Changes:

1) Tidying up text on the admin page.

2) Putting tooltips in the meta box instead of lots of visible text (to tidy up things a bit and avoid repeating the explanation when another input is added for a multivalue field.

3) Full localization into Portuguese.

If this commit is accepted, maybe we should have a different version number? x.x.1?