Further UX related CSS styling fixes

[lgecse]

Further UX related fixes that are a bit more complex to achieve:

• left nav bar background color should be like the footer's:

  • page frame is not filling the whole visible space, on bigger screen this does not look nice out of the box. Might worth to try it with a gradient.

• add right side border line to the left nav bar:

  • main container and header has a gap where this line cannot render anymore. Does not look nice out of the box, further tinkering is necessary.