new syntax for RequiredValidUntil filter

[Rod Widdowson]

> It isn't out of the realm of the possible that we just document this as a 4.0 change and make the change then from seconds to
milliseconds
> for numeric values that nobody should be using anyway.

I'll make that happen.  
 
> Do we get the chance to warn on Duration fields being set by numeric input? I think not because of how Spring works, just
checking.

Yea, we currently do this anyway (down in DurationToLongConverter).  I suspect that it's less liable to false positives than
BooleanToPredicate but that's a known issue.

In this case of course we cannot use the converter, but this means that we can (and do) issue a warn.  And it's very explicit.  As
far as I can remember we have done so since the first V3 beta.

> It is a Duration now, though, isn't it? I'm setting it with that syntax in 3.3 (and going back to older versions).

Yes, it has been since (very) late in V2.  It wasn't old enough in V2 that we could assume that people would have moved up from
seconds.  Anyway we were totally paranoid about not breaking anything we didn't need to.

> I think that's what I suggested above.

Indeed.  To summarise
- I'll rip out this change (plus documentation) and retarget the associated case to be work in V4 to
   o Have this filter on by default
   o Have the default be 14 days
   o Have the validtyUntilDuration be a proper Duration and not a stupid seconds thing

Thanks all