[24apr18]
from website https://github.com/google/googletest/releases
downloaded https://github.com/google/googletest/archive/release-1.8.0.tar.gz
unpacking yields googletest-release-1.8.0
we only use the subdirectory googletest
moved it to ThirdParty/common/gtest/gtest-1.8.0
removed subdirectory samples

[2oct20]
from website https://github.com/google/googletest/releases
download https://github.com/google/googletest/archive/v1.10.x.tar.gz
unpacking yields googletest-release-1.10.0
Due to changes in the cmake machinery, the full folder is used, but googlemock is not needed and removed
move the whole thing (minus googlemock) to gtest-1.10.0
removed subdirectory samples
add modified options to gtest/CMakesLists.txt
