Improved the list element layout

Switched back from flexboxes to ordinary floating elements, so the
elements will be aligned left, even if there are not enough elements in
a row. Previously this wasn't possible due to flexboxes and
justify-content: space-between...
Removed archive file mode calculation for windows

File modes will still be included since the latest grunt-contrib-compress
version, but creating archives for osx and linux while using windows
won't be supported anymore. Too much effort for an unnecessary task...