Fix annoying warnings

[aPruner]

There are on the order of 10 annoying warnings when compiling, the main two are:

C26812 The enum type 'sf::PrimitiveType' is unscoped. Prefer 'enum class' over 'enum' (Enum.3).

and

C26451 Arithmetic overflow: Using operator '+' on a 4 byte value and then casting the result to a 8 byte value. Cast the value to the wider type before calling operator '+' to avoid overflow (io.2).

and the rest are undeclared member variables in various classes.

Fix them!

[aPruner]

Assigning this to @carterkelly9 since it should be super easy! Feel free to create a branch called code-quality/18-fix-annoying-warnings and get started!