Added first UI elements

Rules can be created from the UI
Game can be stopped/started from the UI
Current level can be reset (Load from file again)
Added "Game" target and main file

TODO (A lot):
 - Unit tests
 - Fully functionnal UI
 - Win conditions
 - Level background
 - Level switching/progression
 - Interesting and varied rules
 - Multi-scale pathfinding
 - etc

game/main.cpp

@@ -0,0 +1,15 @@
+//
+// Created by trotfunky on 11/06/19.
+//
+
+#include "Game.h"
+
+int main()
+{
+    std::vector<std::string> textures = {"Head_Boy.png","Head_Significant_Boy.png","Building.png"};
+    std::vector<std::string> levels = {"test_level.xml"};
+
+    Game game(levels,textures);
+    game.loadLevel(0);
+    game.runGame();
+}