Configure environment for Linux.

Server runs ok, the game runs but with no window...

Separate mock library from source.

Implement gamepad logic for macOS.

Add compatibility for macOS and *NIX files

TODO: inspect building of dependencies

Update identifiers to be consistent.

Websockets server is for game networking.

Update input tests.

Add spine-runtimes to dependencies

Make device handling opt-in.

Use bdd-for-c for unit tests.

We use minIni to parse ini files instead of implementing our own. This
is useful for config modifiable by the user, such as controls.

However, we haven't implemented a fault-tolerant config that writes to
the config when the existing file is corrupted or non-existent. We will
have to define a "save" as soon as we have all values defined for our
in-memory config, regardless if we have retrieved the values
successfully or provided default hardcoded values.

Since we use an external dependency to manage our configs, the CMake
config must be modified and the source files included in the build. How
do we organize the dependencies from other Git repositories moving forward?