Add backer_name as filter to find_entities_filtered

[Sandman2003]

The class LuaSurface has a method Find_entities_filtered - it would be useful to enable this to filter based on backer_name (obviously only where backer_name is applicable, so maybe the type has to already define an entity type that supports backer_name). This would reduce needing to deal with over sized datasets when for example looking for specific train stops (stations), or checking for their existence, etc

[Rseding91]

This seems like the completely wrong way to go about finding a train stop by name.

What it sounds like you actually want is a way to get a train stop or stop(s) with a specific name.

[Rseding91]

I've added LuaGameScript::get_train_stops(), LuaSurface::get_train_stops(), and LuaForce::get_train_stops() for 0.17.

[Sandman2003]

Yes I agree (with it is the wrong way), and thanks.