Improvement of loading artworks

[mat]

In my opinion, loading new artworks in a moment of choosing a set isn't always a good thing. For example, if you set Override level graphics to Yes and choose the set with a different graphics than the overridden one, the game will try to load it anyway but the overridden graphics will be left intact. But when you choose a set with the already selected (overridden) artwork afterwards, RND will load it again... It involves also music and sound artworks. The idea is to skip loading new resources unless the settings allow to do it. Graphics is overridden - don't load a new graphics, music is overridden - don't load a new music. Sounds are not overridden by another artwork - load new sounds. If you change not to override graphics and music, then load those new things as long as they are different (also in a moment when the chosen set doesn't use those overridden artworks).