Fix some colors for better readability, fix shadow/halo drawing

- Fix text color of journey route items
- Fix drawing of route stop items on mouse hover:
It could draw light text on a light halo (unreadable)
- Fix unreadable background/text color combinations in journey view.
The positive/negative background colors of the current color
scheme are darkened/lightened to provide enough contrast to the
text color. If the background color gets darkened it's saturation
gets raised to still be able to identify the journey rating easily.
For neutral rating the neutral background color form the current
color scheme gets now used instead of transparent.
- Fix zoom factor update of journey route items, they now properly
update their geometries to zoom factor changes
- Fix enable/disable drawing of shadows/halos