Add more Lua functions

Added more Lua functionality:
- Actor property "InfoName" (probably not the best name, might just want "Name" or "Type") to get the actor type (e.g. E1)
- Player property "PlayerName" (same as old Lua) to get the player's name (e.g. hamb)
- A ctor for WRange (this is required to use Map.ActorsInCircle)
- Modify ActorsInCircle to accept a `nil` filter
- Add Guard to the Combat functions (not sure if this is in the right place)
- Map.NamedActor now returns `nil` if the actor is Destroyed

I'm more interested in a review right now rather than a merge, because there ~~might~~ will be more I add (or maybe that's another PR). If we're happy I can provide a test map using these functions for reviewers.
I guess you could have left that class in CombatProperties.cs (and in the property group "Combat") as well. But if I'm not mistaken, the property groups are mainly used to create the tables for the wiki docs, and (maybe?) as an argument for the HasProperty function, so it's not a big deal.