Add WMS support to layer manager, simplify layer creation
Add some logging to picking manager
First draft of multiple conxtexts : planet & sky, in one application
  * Use of two different canvases. TODO: try to use only one
Fix planets visibility
  * Update ephemeris data for planets
  * Make planets pickable
  * Simplify picking manager code
Hide unused in planet-mode buttons
Fix shared parameters, turn continius rendering to false
Fix some layout issues
  * Selectmenu height
  * Display planet name in popup list
Add compass & image viewer gui on initialization
Fix aborted image method, update GlobWeb snapshot
Use only one canvas for rendering, add mechanism to hide/show UI composants on context toggling