Since the most drawing params can be changed via menu or shortcuts, remove default.css and user.css.
* Missing params like palettes, dash, grid, etc, are added to prefs.
* Add palette choice to menu and shortcuts.
* Some defaults like fonts, line width, etc, are no longer modifiable by the user.
Keybinding to ungrab keyboard and mouse while drawing remains at the top.
To be aware that this create some problems with the shell (DnD #1 and maybe more ?).
related to #6, #9, #20, #24, #33
* `SCALE_PRESERVE` (preserve ratio)
* `SCALE` (vertical, horizontal or both)
There is a third transformation, `SCALE_ANGLE`, that is not used because it causes problems to the `elementFinder`. Probably a bug of Cairo.inStroke that do no consider scales.
* 'Shapes' -> 'Tools' ('Shapes' + 'Manipulations')
* 'TextState' -> 'TextStates'
* Rotation centers are now computed dynamically (when building Cairo or SVG paths).
* Text rotation center is now located at the beginning of the text.
* Text elements gain a 'lineIndex' attribute to retrieve the rotation center of the first line.
* Use a "drawOnYourScreen" subdir in the xdg user data dir
* Info item with the name of the last saved/open json file
* "Open drawing" sub menu with data dir content
* "Save drawing" sub menu with entry
* "Save", "Open previous" and "Open next" keybindings