freifunk-berlin-migration: first draft for migration script
freifunk-berlin-migration: refactor migration script

This should contain all migration steps for 0.1.0:

* dhcp leasetime
* htmode change to HT20
* openvpn remote dns change
migrate luci_statistics
remove wrong settings from collecd and rrdtool
updated comments some comments and log messages
freifunk-berlin-migration: add semver.sh licence header
Merge branch 'migration'