JBIDE-18670 HTML5 Palette: Palette model refactoring

new palette model implemented
Well, both my comments to this got obsolete and unanswered. That is not nice. I have to repeat it here.

After fix in getSelectedVersionGroup() that now throws exception I am sure it is better to do search in setSelectedVersion and keep selectedVersion not as string but as IPaletteVersionGroup. Accordingly, throw IllegalArgumentException in setSelectedVersion if group is not found.

So, selectedVersion should be of type IPaletteVersionGroup found in setSelectedVersion and getSelectedVersion should just return it.