add licence header

CMakeLists.txt

cmake/CodeCoverage.cmake

cmake/FetchGTest.cmake

doc/CMakeLists.txt

doc/api/header_file.rst.in

doc/api/index.rst

doc/index.rst

include/CMakeLists.txt

include/caosdb_config.h.in

include/connection.h

src/CMakeLists.txt

src/caosdbcli.cpp

src/connection.cpp

test/CMakeLists.txt

test/test_connection.cpp