Select multiple layers by ctrl+clicking them #1157
Hi @Kiloku, actually you can do something like that using the Move tool when several layers are selected in the Timeline: http://www.aseprite.org/docs/move-tool/#move-multiple-cels
The problem is that I can't select multiple layers that are not adjacent on the list of layers. The only way to select multiple layers (that I know of) is dragging the selection, which forces me to handle all layers in between the ones I want.
This is what I mean (I want to select the "Braco" and "Face" layers, but not any of the others)
Changes: * With this patch we finally removed the LayerIndex class and member functions to access layers by index (like Sprite::firstLayer/layerLayer /layer/indexToLayer/layerToIndex() etc.). As layer groups can be expanded/collapsed, it doesn't make sense to use layer index to access layers directly from sprite. * Now we use a layer_t (int) to access a list of browsable layers each time we want to iterate visible layers in the timeline. * Replaced CelsRange() and Sprite::uniqueCels() param with SelectedFrames to iterate non-adjacent cels. * Updated clipboard operations (copy/paste) in timeline to support layer groups. * Updated Timeline control to support selecting multiple layer/frame ranges with Ctrl+ or Alt+click (fix #1157) * Added more test units for DocumentRange operations (mainly for non-adjacent ranges).