Editor: clicking on "missing event function" warning should bring up the related object's events table

[ivan-mogilko]

After #2556 Editor throws warnings about events that have function names in them, but no actual function defined in script.
These warnings mention object's name, but it would be more convenient if user could double click on it to bring this object up for editing, similar to how you can double click script error to bring up the line in script.

For this to work, we might need a new subclass of CompileMessage, which has something like following:

• object's script name (it's unique in global/room namespace);
• object's typename and id (because script names are not obligatory, sadly);
• parent's identifier, which may be either a gui script name for the gui control, or a room number of anything in the room.

The "Goto definition" menu command already supports going to a global object, that functionality may be shared to some extent.
Going to the rooms will require opening that room. Currently editor only supports opening 1 room at a time, so preferably it should ask if it's okay to load a new one would another be open at the moment.