Add method to move entity from one entity manager to another

I'm using the entity manager class for all entities that are currently loaded into the game, as it has many useful features for querying entities with specific components. However, I often find myself having to create entity vectors in order to know what entities I should be querying based on where somebody currently is in the game, which obviously ends up leading to me re-creating querying this structure. I think there would be a lot of use for this if it were added in