contrib/meshwizard: make gen_bssid create BSSIDs that are valid according to the 80211 standard. This also makes it possible to merge the general BSSID scheme with the pberg bssid scheme. Thanks stargieg.

git-svn-id: http://svn.luci.subsignal.org/luci/trunk@9577 ab181a69-ba2e-0410-a84d-ff88ab4c47bc