Fix navigation blueprint dropdown hover
Fix navigation blueprint dropdown hover

Use more restrictive CSS rules in order to apply rules only in the
nav bar. Fix gap between navigation item and its dropdown menu.

agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,agdsn/pycroft,lukasjuhrich/pycroft