With old GS/GJS, some GType names were generated from class names without sanitizing it (e.g. Menu.ActionButton).
Instead of defining all GType names, sanitize all class name as it was GType name, and let GJS generated GType name securely when it is necessary.
Fix#46.
* Import palettes from a .gpl file (one palette for each column).
* Add possibility to use more than 9 palettes.
* Color display names support.
* color.toJSON for svg and drawing saves, color.toString for display.
use `PangoCairo.show_layout_line` instead of `PangoCairo.show_layout`. It is equivalent.
show_layout (doc): "The top-left corner of the PangoLayout will be drawn at the current point of the cairo context."
show_layout_line (doc): "The origin of the glyphs (the left edge of the line) will be drawn at the current point of the cairo context."
So it is no longer necessary to query `layout.get_baseline()`.
* Group "transform" attributes.
* Round "transform" attribute values.
* Remove unused stroke attributes.
* Add an "eraser" class attribute to let user retrieve the element role.
* Pass Clutter color and Pango fontDescription objects to elements, not strings.
* Do not use the color format '#rrggbbaa' in svg since it is not supported in GNOME 3.24.
* It is no longer required to clamp the setting value in area.js.
* Add a "range" property, completed with another 'step' property, to PixelSpinButton in order to directly initiate the lower and upper values of the adjustment from the relevant setting range.
* Not related: fix an inversion between Pango and Cairo in element.js.
abakkk