Merge GUI and CLI executables

[calcmogul]

We want to make the main GUI executable support CLI arguments. We had to split them up because Windows wasn't redirecting stdout properly in the CLI app when the console is deallocated (we do that so the GUI doesn't also open a console window).

Our options are have an attached console that will kill the application when closed, or have no console and redirect all stdout to a file. std::freopen() (C++) or libc::freopen() (Rust) can theoretically do this.