add player compatibility api (#41)

src/player/xcompat_agnostic.lua

@@ -0,0 +1,41 @@
+local papi = {}
+
+local models = {}
+function papi.register_model(name, def)
+    models[name] = def
+end
+
+function papi.set_model(player, model_name)
+    local model = models[model_name]
+
+    if not model then return end
+
+    player:set_properties({
+        mesh = model_name,
+        textures = model.textures,
+        visual = "mesh",
+        visual_size = model.visual_size,
+        stepheight = model.stepheight
+    })
+end
+
+function papi.get_animation(_)
+    --stub to keep from crashing
+end
+
+function papi.get_textures(player)
+    return player:get_properties().textures
+end
+
+function papi.set_textures(player, textures)
+    player:set_properties({textures = textures})
+end
+
+function papi.set_animation(_, _, _, _)
+    --stub to keep from crashing
+end
+
+--nothing to do here as we have no globalstep .....that we know about anyways
+papi.player_attached = {}
+
+return papi