Contact details: add option to make email private

[andibraeu]

• maybe don't send email address to libremap
• don't show email on contact page

[andibraeu]

as mentioned, there's some more work needed in router packages to hide email from contact page and don't send it to the map:

needs work on https://github.com/freifunk-berlin/firmware-packages/tree/master/utils/luci-app-owm
maybe you can use something like that: weimarnetz/openwrt-packages@2817569

[sarumpaet]

freifunk-berlin/firmware-packages#92 made the coupling of owm.lua and OpenWifiMap less tight; it's trivial to transparently replace the email address by a link to a web form now as well (for Berlin). I guess this is what most people will want: A simple way to get contacted, but not exposing the e-mail address to spammers. Perhaps add an option for that as well?