Merge branch 'CI' into 'master'

.gitlab-ci.yml

CI/ci-linux.sh

CI/ci-mac.sh

CMakeLists.txt

cmake/ACGCommon.cmake

cmake/FindGoogleTest.cmake

src/ExactPredicates.hh

src/FileAccessor.cc

src/Matrix4x4T.hh

src/predicates.c

tests/CMakeLists.txt

tests/cellextraction_test.cc

tests/common.cc

tests/common.hh

tests/fileaccess_test.cc

tests/gridisomorphism_test.cc

tests/navigation_test.cc

tests/predicate_test.cc

tests/testdata/cylinderadvanced.hexex

tests/testdata/fiveFine.hexex