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.
You need to do the Guard lookup on the actor doing the guarding.