Use full string for sidFuel and avoid string concatenation Fuel as in fuel for saucer, landgun, flamethrower, icegun. Old string was built with like this: sidFuel + ": " + fuel + "%". New string us built with proper format string instead

Directory for automated tests to test the engine.

Run `ctest` in the root directory of this repository to run all tests.
Run `ctest -R <test name>` to run only the test with the given name.

This requires you to have CMake.