Feature Request: Show Announcements in icingaweb2 after upgrade

[bebehei]

Currently the image does not update /etc/icingaweb2 and /etc/icinga2 after docker pull and container-restart. So icingaweb2 and icinga2 do not get fresh and neccessary configuration, which might be needed to fix some bugs.

I would propose to add some add "VERSION"-file (e.g. /etc/icingaweb2(.dist)/VERSION), which holds an integer number. And as long the integer of /etc/icingaweb2/VERSIONis less than/etc/icingaweb2.dist/VERSION`, a script creates an announcement in icingaweb2. So we could remind the user to manually merge the new changes.

The announcement would be placed in /etc/icingaweb2/announcements.ini and could be easily added by either just appending via echo/cat or using or using ini_set introduced in #67.

If we add tags on every configuration-change, it would be easily possible to also add an autogenerated link like: https://github.com/jjethwa/icinga2/compare/config-v1...config-v2

[bebehei]

Fixed in dedbb7c