widget handler: refactoring: - replaced proof of concept implementation with cleaner one based on custom layout - removed proof of concept big bars in favor of thin line to separate widgets, with a 3 dots area in the center where user can touch/click more easily - when in delete zone, the line + half circle become red, so user knows that she's about to delete a widget - carousel is now created in kv - ignore perpendicular swipes. This was not working before but is know working well, and the swipe is far more easy to do on desktop or mobile - each new widget of the handler has an id (its creation number), which is displayed in debug logs on touch - handler's widgets keep track of which widgets are on sides (left, top, right, bottom)