Add options to control the cmake process, to make it easier to include from a
parent cmake project.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge branch 'cmake_options' of https://github.com/hpcc-systems/cpp-driver into hpcc-systems-cmake_options
Removed cmake message() call
Merge branch 'hpcc-systems-cmake_options' into 1.0