Expaneded the lua API for Regions

I've added lua hooks for both pager functor classes. Hopefully, I haven't
missed any corner cases, because it took me a while to hunt everything
down. One issue is that the map's save directory needs to be set in the
Format class, but it'll do for now. I'll review this again when I've got
more than one map running at one time.

There should be enough here for a lua-driven map generator to be
implemented, even if it's a bit rough. I think I'll test this out in the
editor eventually, but getting the base branch's network map code going
comes first.

The current process is extremely convulted, so I need to document
everything that I've done so far, including C++ and lua functions.

common/map/map_generator.cpp

@@ -21,6 +21,8 @@
 */
 #include "map_generator.hpp"
 
+#include <stdexcept>
+
 void BlankGenerator::Create(Region** const ptr, int width, int height, int depth, int x, int y) {
 	(*ptr) = new Region(width, height, depth, x, y);
 }
@@ -38,14 +40,29 @@ void PerlinGenerator::Unload(Region* const ptr) {
 }
 */
 void LuaGenerator::Create(Region** const ptr, int width, int height, int depth, int x, int y) {
+	//something to work on
 	(*ptr) = new Region(width, height, depth, x, y);
 
-	//generate the lua-driven maps
-	lua_getglobal(state, "CreateRegion");
+	//API hook
+	lua_getglobal(state, "Region");
+	lua_getfield(state, -1, "Create");
 	lua_pushlightuserdata(state, *ptr);
-	lua_pcall(state, 1, 0, 0);
+	if (lua_pcall(state, 1, 0, 0) != LUA_OK) {
+		throw(std::runtime_error(std::string() + "Lua error: " + lua_tostring(state, -1) ));
+	}
+	lua_pop(state, 1);
 }
 
 void LuaGenerator::Unload(Region* const ptr) {
+	//API hook
+	lua_getglobal(state, "Region");
+	lua_getfield(state, -1, "Unload");
+	lua_pushlightuserdata(state, ptr);
+	if (lua_pcall(state, 1, 0, 0) != LUA_OK) {
+		throw(std::runtime_error(std::string() + "Lua error: " + lua_tostring(state, -1) ));
+	}
+	lua_pop(state, 1);
+
+	//clean up the memory
 	delete ptr;
 }