Marble: Refactor planet rendering code
completed by: Illya Kovalevskyy
mentors: Torsten Rahn, René Küttner
Recently rendering of the planets has been introduced in Marble master.
However the code contains a lot of redundancy and copied code.
The code should be refactored so that the same code is executed for all planets (except for the Sun and Moon) inside a for loop.
At the same time the amount of planet specific members should be reduced: In order to store the state for availability inside the for loop, an array needs to be created. This will probably also require the creation of an enum. This would also allow for easier configuration saving which should be refactored at the same time.