contrib/meshwizard: Move the check if VAPs are supported in a seperate script so we can reuse it later by luci-app-meshwizard, also check if hostapd[-mini] is installed when using mac80211

git-svn-id: http://svn.luci.subsignal.org/luci/trunk@9612 ab181a69-ba2e-0410-a84d-ff88ab4c47bc