Maybe add prefix for all defined cmake build options?

[german3w1]

Hi, @Enmk!.
I noticed that all the build options in the root CMakeLists.txt do not have any prefixes to ensure that they do not overlap with other project options when included as a dependency.
How about sacrificing a little backwards compatibility and adding the prefix CLICKHOUSE_CPP_ to the name of each option (in the YAML_CPP library its authors went exactly this way, for example)

Example for clickhouse: BUILD_TESTS -> CLICKHOUSE_CPP_BUILD_TESTS

I'll do this if you find the idea is worth

[Enmk]

Sure, let's do it! I think that this might be a good idea for a 3.0 release.

[Enmk]

Fixed in #360