Created dynamic palette displaying currently used colors.
This palette is now selected by default.
New service UsedColorsService created. Listens to PISKEL_RESET and
TOOL_RELEASED and keeps track of the list of current colors.
Still need to :
- improve sorting of colors
- allow to clone the current color palette as a custom palette
- add proper getter in UsedColorService to get the list of current colors
Also I hardcoded a max-height for the palettes-list as I found no better
way of handling the case of palettes containing many colors.
Maybe should add a limit to the number of colors handled by this automatic
palette.
- Fixed : manager UI is redrawn after save
- the Selected palette is saved as a user preference
- default background is now the dark one
- the selected palette is not reset after closing palette manager
