Add cmake find module

# FindGDCPP.txt

#

#     Author: Fabian Meyer

# Created On: 05 Aug 2019

#

# Defines

#   GDCPP_INCLUDE_DIR

#   GDCPP_FOUND

find_path(GDCPP_INCLUDE_DIR

    HINTS

    ${GDCPP_ROOT}

    ENV GDCPP_ROOT

)

include(FindPackageHandleStandardArgs)

find_package_handle_standard_args(GDCPP DEFAULT_MSG GDCPP_INCLUDE_DIR)