Rework layouts: Layout is now normal Container which places its children upon resize event.
Drop TopWindow, top is now any subclass of Container.
Add floater concept: floaters are widgets drawn over normal widgets, not clipped by parent.
Add HScrollbar and Scrollbar abstract base class.
Colors
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backend.setcolor(name, description)
This will parse description, prepare attributes and save them under 'name'.
Description is in format <foreground> "on" <background> "," <attributes>.
For example:
"black on cyan"
"white on cyan" or "gray on cyan, standout" (equivalent)
"yellow on red, underline, blink"
backend.pushcolor(name)
backend.popcolor()
Default theme
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menu-normal - black on cyan
menu-highlight - white on cyan
window-normal - gray on blue
window-highlight - white on blue