Hide fuzzy translations from the web UI

We should hide fuzzy translations from the web UI, and only use them to reconstruct imported PO files when needed (i.e. on export, or when importing a newer PO file from upstream).

'Needs review' checkbox should be visible only to reviewers (and it would make their translation be submitted as a suggestion, and not activated: it would have nothing to do with the 'fuzzy' flag), 'with new suggestions' filter should be renamed to 'needs review', and fuzzy translations should be completely hidden from the web UI (the reason being that they are a really bad similarity match in most of the cases, and where they aren't, they have usually been fixed upstream already: once we implement proper translation memory suggestions [fts on msgids? see rosetta-fuzzy-merge spec], we'll have the needed features without having to play with the fuzzy flag).

For PO files uploaded by reviewers, we may want to consider using fuzzy flag as the mark of "Please review this" and add that message as a new suggestion instead of setting it as a current translation directly.