debian: Remove all useless stuff from debian/rules, force cmake buildsystem

The top-level makefile that was used to drive cmake broke the autodetection
of the used buildsystem by debhelper. This commit fixes it and moves most
of the installation stuff to CMakeLists.txt to keep debian/ folder contents
to the bare minimum.

Signed-off-by: Andrew Andrianov <andrew@ncrmnt.org>