Fix logrotate, refine postrm, prerm script to ensure config and log files removed after purged. (Closes:#851356)

disable-slp.patch: do not use SLP in obs-serverconf as Debian drop slptool from archive. (Closes: #848855)

Refine postinst script to avoid modifies some files it has shipped. And also not fails during installation without setup database via dbconfig-common. (Closes: #847687)

As much as I think that it is nice to have OBS in Debian, I cannot
commit to maintaining it.

user purged these packages.

debian/control: depends on default-mysql-client and recommends on default-mysql-server as the old package name has been obsoleted.

debian/control: obs-server shouldn't depends on obs-api. It should be able to install independently.

debian/control: move sphinxsearch deps from obs-server to obs-api as it's needed search function for the webui instead of backend server.