Minor adjustments and optimizations

[list] [*] Click priorities adjusted. Especially if you place several rooms on top of each other and use Deco Images. [*] Working in general with stacked rooms improved. For example, you can no longer accidentally click on an object on the first floor through a room above it. [*] “Layers” renamed to ‘Groups’. (These are not classic layers as known from image editing programs, but optional and do not affect the height of the objects. This may have been confusing) [*] Minor things and bug fixes [/list]