More Imp needed to be encapsulated to decouple history/info dat lookup

So it will be the next commit that re-implements the parent lookup now....
Imp of parent history dat lookups now uses correct algorithm via function call

We look through dat for child, then we look through for parent
tidyup
Refactored for MameInfo and MameHistory sharing the same code

There was much repitition, and Info needs to lookup parent if child isn't found, just like the history dat (it does in MameUI)