Apache 2.4 transition

This uses the newly introduced dh_apache2 helper to install the apache
config file. The file is installed to /etc/apache2/conf-available and
enabled by default.

Closes: #669834
Use doveadm pw instead of dovecotpw by default

Closes: #706698
Change Vcs-Browser for new cgit interface

Git-Dch: ignore
Merge pull request #1 from gaudenz/master

Apache 2.4 transition and Bugfix for #706698