Extract tests from source directory.

Remove old SDL dependency.

Add correct includes.

Put mocks to directory structure mimicking project structure.

Use CMake definitions to specify config paths and filenames.

Put input and video subsystems into their own directories.

Ensure no side effect persists when errors have been triggered.

Update documentation.

Attempt to connect client to server.

Add memory and data-related implementations for handling game data.

Properly mock video function dependencies.

Correctly dereference pointers.

Ensure correct arguments are passed.

Ensure one type of test can only be handled at a time.