See map.h changes to see why this makes this cleaner.

This is a very common pattern in practice -- and annoyingly difficult with STL maps.

This required some refactoring so than index.insert() could be called before the row was actually constructed, based on the search parameters.

It also required some awful hacks to support putting the creation function at the end of the argument list to findOrCreate(), with a variable-width arg list before it.