CMake packaging improvements

[daneos]

I started working on Debian packaging for the clickhouse-cpp library (not officialy, I need the packages for internal use) and I made some improvements to CMake setup that makes it play nicely with packaging tools.

I thought some of them can be useful for the project.

I tried to split my changes into logical commits so that it's easy to cherry-pick a subset of the changes.

Apparently also closes #105

[CLAassistant]

All committers have signed the CLA.