ADDED: Network - Basic network support.
ADDED: Screens - Screen system that manages screen transitions.
ADDED: Screens - Login screen.
ADDED: Network - Showing error message in case of an login failure.
ADDED: Network - Login screen indicates progress.
ADDED: Network - Switching to game screen after successful login.
FIXED: Core - Event manager no longer stores listeners as shared pointers, as these created a second ownership group and caused objects to be deleted while others were still trying to access them.
ADDED: Project - Reference to static network library.
ADDED: Network - Queue for receiving network packets.
CHANGED: Project - Moved core classes into own project and referenced it.
ADDED: Network - Receiving packets from the server, and sending packets on tap.
ADDED: Network - ClientActionWriter and ServerEventReader classes abstracting reading and writing data from DataReaders and DataWriters.
FIXED: Network - ClientActionWriter no longer returns a value.
Merge branch 'feature/networking' into develop