Tricky changes to the stylesheet to allow black background in the outline pane:

Added the following settings:

- @color head-fg = black
- @color edit-label-fg = black

Removed the following settings:

- tree-item-selected-bg: use edit-label-bg instead.
- tree-sel-bg: used edit-label-bg instead.
- tree-sel-fg: used edit-label-fg instead.
- edit-label-border.
- edit-label-margin.

Replaced entire QLineEdit#editorLabel style specifier by the QTreeWidget::item:selected specifier.

Leo build: 20141205060357