buildcert: add basic cert-sign example - taken from https://gist.github.com/ril3y/1165038
buildcert: add basic cert-sign example
- taken from https://gist.github.com/ril3y/1165038

freifunk-berlin/ca.berlin.freifunk.net,freifunk-berlin/ca.berlin.freifunk.net,freifunk-berlin/ca.berlin.freifunk.net