enclose CMAKE_BUILD_TYPE in quotes; this transforms it into an wmpty
string and the string command wont complain that its missing an argument
when CMAKE_BUILD_TYPE is not set.

Cmake treats CMAKE_BUILD_TYPE string as case insensitve. Make the check
for enabling coverage reflect this to make usage less restrictive.

fix issue that a double "-l" can appear in the Makefile config shell scripts for libraries which already contain the -l

usage:
register_tests(SOURCES
                 ${list_of_source_files}
                 "test_src.cc"
                 ${concatenated_string_of_source_files}
               NAMESPACE
                 "test_namespace"
               LINK_LIBRARIES
                 ${list_of_targets}
               INCLUDE_DIRECTORIES
                 ${list_of_include_directories}
               COMPILE_OPTIONS
                 ${list_of_compile_options}
               WORKING_DIRECTORY
                 ${ctest_working_directory})

Introduced cmake module registerTests:

new scheme:
register_tests(SOURCES
                 ${list_of_source_files}
                 "test_src.cc"
                 ${concatenated_string_of_source_files}
               NAMESPACE
                 "test_namespace"
               LINK_LIBRARIES
                 ${list_of_targets}
               INCLUDE_DIRECTORIES
                 ${list_of_include_directories}
               COMPILE_OPTIONS
                 ${list_of_compile_options})

usage:
register_tests(SOURCES
                 ${list_of_source_files}
                 "test_src.cc"
                 ${concatenated_string_of_source_files}
               NAMESPACE
                 "test_namespace"
               DEPENDS
                 ${list_of_targets}
               INCLUDES
                 ${list_of_include_directories}
               COMPILE_OPTIONS
                 ${list_of_compile_options})

Function registers tests defined as a list of souce files.  Test defined
by file source_name.cc in the SOURCES list is registered under the name
  test_namespace.source_name

Provided list of dependent targets and include directories are used for
test executables as PRIVATE dependencies during compilation.

Function implicitly adds a dependency on the boost unit test framework
to each generated test executable.

This reverts commit 7eace484.

GNUInstallDirs doesn't really deliver the intended directories. CMAKE_INSTALL_LIBDIR e.g. points to lib/x86_64-linux-gnu on Ubuntu 16.04

Not adding the repository as a remote simply makes it impossible to push
to it. Also this makes it mandatory to always fetch the changes from the
remote anyway since it is not locally mirrored.

add enable_latest_cxx_support.cmake and added a comment to enable_cxx11_support.cmake to no longer use is.

Ignore configuration files for Visual Studio Code.

also export the LIBRARY_DIRS variable to the calling CMakeLists.txt (needed to publish it to further downstream dependencies)

Fixed the confusing and inconsistently used names *_LINK_FLAGS and *_LINKER_FLAGS by always setting and getting both variables