#476 Use tags for matching objects

[Sebastian Andersson]

If sending just a number to object_matches_string, this change makes the function compare the number with the object's tag.

This is useful if you want to add more menu commands for objects in a client, for example adding a "empty" to the menu for containers. Then you don't want to match the other containers with the same name.

[Kevin Zheng]

Committed in 1254bce3a with minor changes, thanks!