Add CMake option for disabling benchmark build

[Shibodd]

I don't need to build the benchmarks, but their build fails even if benchmark_FOUND is true on my system (fatal error: benchmark/benchmark.h: No such file or directory). Most likely it is a broken system on my part.

Building only the data_tamer target is fine, but the install target also builds the benchmarks. This requires me to patch the CMakeLists.txt.

Add a CMake option for disabling benchmark builds like there is for examples and tests - it doesn't make much sense not to have it.