Client builds & runs, can't test the gameplay without the server

SDL_ttf is now being initialized, and all usages of fonts are now checked for nullptr.
A bug where the renderer's logical size was not properly set has been fixed.
The FPS counter is disabled for now.

client/client_application.hpp

@@ -27,6 +27,8 @@
 #include "udp_network_utility.hpp"
 
 #include "SDL2/SDL.h"
+#include "SDL2/SDL_net.h"
+#include "SDL2/SDL_ttf.h"
 
 class ClientApplication: public Singleton<ClientApplication> {
 public: