Add sound-rel as copy of bfsc

sound-rel.de website for initial development. Will later be transferred to
other server and thus repository.

This is a copy of the current state of beautifulscores.net
snd: Change structure and make empty stubs
snd: Change Font to Cabin
snd: Adjust menu bar font weight
snd: Remove bfsc logo file
snd: Add logo SVGs
snd: Change some color settings (WIP)
snd: Style preliminary header
snd: Fix footer details
snd: Initial Home page content
snd: Change section titles (add "Serie XX")
snd: syntax detail in header template
snd: Add conctact/order page (de/en)
Merge branch 'sound-rel'