Fix data directory path example for Linux

See http://docs.geoserver.org/latest/en/user/datadirectory/data-dir-creating.html for how this gets rendered.
Merge pull request #831 from bradh/patch-4

Fix data directory path example for Linux
fix copyright in conf.py files
Fix a few headers that got left out in the cold
Merge remote-tracking branch 'upstream/master'