Drawing 0.6.0 but with more appstream-util idiotic requirements

• remove the "windows" menu from the menubar
• refactor bottom panes management to allow several tools to share the same pane
• rectangle selection, freehand selection, and color selection, are now distinct tools
• the 'rotate' tool now handles horizontal or vertical flipping
• the 'rotate' tool now supports any angle when rotationg the selection
• the tools producing shapes (circle, rectangle, polygon, …) are merged into a single 'shape' tool
• "close shape" action for the 'shape' tool
• "close selection" action for the 'free selection' tool
• replace the 'saturate' tool by a new 'filters' tool
• add several types of blur to 'filters'
• add color inversion, pixelisation, partial transparency to 'filters'
• add "additional tools" section to the preferences window
• add specialized types of pencils (eraser, highlighter) as optional tools
• a fullscreen mode is now available
• zoom in (or out) using the minimap, the touch gestures, the mouse wheel, or keyboard shortcuts
• move the "color application mode" selection to the colors menus/popovers
• add "antialiasing" option to several tools
• warn the user when they try to save despite the current operation not being applied
• rewrite the user help manual

and mainly:

• replace the elegant transparent backgrounds around screenshots by hideous black pixels, because it's how we get an elegant and consistent software center.