newToOldCategory in Database.cpp

This appears to be to allow loading pre-version6 databases, where "Persons" was renamed to "People"
and "Locations" to "Places".  But I can't find any code that actually uses it; neither caller to
createImageInfo passes anything in here.

Is that a bug, or is this something I can remove?  There's some cleanup I want to do in
possibleLoadCompressedCategories() that might give us a little bit of improvement, but the
newToOldCategory might get in my way a bit.  It's not going to be a huge improvement; those are
likely to be hard to come by without a faster parser, but everything we can squeeze out in startup
is a good thing (startup is very noticeable).