Entity storage and management

Without proper management, these entities are just random classes scattered about in your memory with no rhyme or reason. In order to produce a robust way to create interactions between entities, they need to be babysat by a manager class. Before we begin designing it, let's define some data types to contain the information we're going to be working with:

using EntityContainer = std::unordered_map<unsigned int,EntityBase*>;
using EntityFactory = std::unordered_map<EntityType, std::function<EntityBase*(void)>>;
using EnemyTypes = std::unordered_map<std::string,std::string>;

The EntityContainer type is, as the name suggests, a container of entities. It is once again powered by an unordered_map, which ties instances of entities to unsigned integers that serve as identifiers. The next type is a container of lambda functions that links entity types to code that can allocate memory and return instances of classes that inherit from the base entity...