Add EntityPotion property for dEntities
Fix <e@entity.has_effect[<effect>]>

I wonder who could've broken this...
Heh...
Merge pull request #676 from Morphan1/master

Create features for non-existing features that don't exist
Merge pull request #675 from mcmonkey4eva/master

Pull request for tiny fixes
fix is_npc, add util.npc_is_valid, fix bugs

- is_npc and is_player should both return true for dPlayer/dNPC's
always, even if they aren't spawned.
- added util.npc_is_valid so people don't have to check if
server.list_npcs contains the NPC or other hackish solutions.
- Fixed some misdefined meta
- caught a potential bug in dEntity, better debug warning for it.