Add MP.Get (#369)

Adds `MP.Get(ConfigID)` to the lua api to get the current server
settings.

```lua
lua> print(MP.Get(MP.Settings.Name]))
[LUA] BeamMP Server
lua> MP.Set(MP.Settings.Name, 'Hello World')
[INFO] Set `Name` to Hello World
lua> print(MP.Get(MP.Settings.Name))
[LUA] Hello World
```

Closes #146

include/LuaAPI.h

@@ -37,6 +37,7 @@ namespace MP {
     std::pair<bool, std::string> SendChatMessage(int ID, const std::string& Message);
     std::pair<bool, std::string> RemoveVehicle(int PlayerID, int VehicleID);
     void Set(int ConfigID, sol::object NewValue);
+    TLuaValue Get(int ConfigID);
     bool IsPlayerGuest(int ID);
     bool IsPlayerConnected(int ID);
     void Sleep(size_t Ms);

src/LuaAPI.cpp

@@ -292,6 +292,28 @@ void LuaAPI::MP::Set(int ConfigID, sol::object NewValue) {
     }
 }
 
+TLuaValue LuaAPI::MP::Get(int ConfigID) {
+    switch (ConfigID) {
+    case 0: // debug
+        return Application::Settings.getAsBool(Settings::Key::General_Debug);
+    case 1: // private
+        return Application::Settings.getAsBool(Settings::Key::General_Private);
+    case 2: // max cars
+        return Application::Settings.getAsInt(Settings::Key::General_MaxCars);
+    case 3: // max players
+        return Application::Settings.getAsInt(Settings::Key::General_MaxPlayers);
+    case 4: // Map
+        return Application::Settings.getAsString(Settings::Key::General_Map);
+    case 5: // Name
+        return Application::Settings.getAsString(Settings::Key::General_Name);
+    case 6: // Desc
+        return Application::Settings.getAsString(Settings::Key::General_Description);
+    default:
+        beammp_warn("Invalid config ID \"" + std::to_string(ConfigID) + "\". Use `MP.Settings.*` enum for this.");
+        return 0;
+    }
+}
+
 void LuaAPI::MP::Sleep(size_t Ms) {
     std::this_thread::sleep_for(std::chrono::milliseconds(Ms));
 }

src/TLuaEngine.cpp

@@ -910,6 +910,7 @@ TLuaEngine::StateThreadData::StateThreadData(const std::string& Name, TLuaStateI
         mEngine->CancelEventTimers(EventName, mStateId);
     });
     MPTable.set_function("Set", &LuaAPI::MP::Set);
+    MPTable.set_function("Get", &LuaAPI::MP::Get);
 
     auto UtilTable = StateView.create_named_table("Util");
     UtilTable.set_function("LogDebug", [this](sol::variadic_args args) {