Added default colors for `Document Map` (pkulchenko/ZeroBraneStudio#339).
Improved scrolling on Windows for `Document Map` (pkulchenko/ZeroBraneStudio#339).
Added switching focus to editor (needed on OSX) for `Document Map` (pkulchenko/ZeroBraneStudio#339).
Fixed jumps during scrolling for `Document Map` (pkulchenko/ZeroBraneStudio#339).