Fixes broken labels in file explorer and manage files view.

Adds a new sass mixin "label" and uses it for single line fixed-width labels.
Makes files and entries in Files Explorer scrollable via overflow: auto.

File explorer is always full height. Some changes in html and css to make sure the height of the containing div is correct.
do not create new nested theming when updating account (#38)

update theme in account's default_theming instead.
Merge pull request #39 from tf/tf-nested-theming

Do not create new nested theming when updating account (#38)
Merge pull request #37 from kioopi/file_explorer_fixes

Fixes for the "Wiederverwenden" File Explorer