Dependent compilation of tests, examples ... etc

[greole]

Turn of build of optional yap parts (tests, examples, ...) see #99.

[greole]

Ok this took me a while to make it work. The tests, example and benchmark can be turned off setting

 -DYAP_BUILD_TEST=OFF
 -DYAP_BUILD_EXAMPLE=OFF
 -DYAP_BUILD_PERF=OFF

In the process I found several issues that I needed to resolve to make the build process more robust. This includes

• Fixing the compilation order by setting add_dependencies so that cmake can figure out the build order.
• Using a newer version of google benchmark, since version 1.2.0 did not compile with the most recent gcc version
• Setting the required C++ by requesting compiler features and letting cmake figure the required compiler flags.

In addition to the last point, CMake can also detect optional compile features using the write_compiler_detection_header function which could set-DBOOST_NO_CONSTEXPR_IF and clean up the main CMakeLists.txt a bit more. But I guess this should be a separate PR.

[tzlaine]

Ha! I just asked for a PR for this in the ticket you opened, and here it is already ready. LGTM.