add removeVariablesFromConnections test for dangling connections
add removeVariablesFromConnections test for dangling connections

nickerso/libcellml,cellml/libcellml,cellml/libcellml,hsorby/libcellml,MichaelClerx/libcellml,hsorby/libcellml,cellml/libcellml,cellml/libcellml,hsorby/libcellml,libcellml/buildbot-testing,MichaelClerx/libcellml,MichaelClerx/libcellml,libcellml/buildbot-testing,hsorby/libcellml,nickerso/libcellml,nickerso/libcellml,nickerso/libcellml