Added libtool built libcdi.so to python interface creation
python interface itself is not built with libtool, yet

Configure gets triggerd by CDO's configure call for non installing libcdi.la
through a shell variable, so '--enable-cdi-lib' is removed (refs #492)

This is the default build for CDO. 'make distcheck' still checks 
building + installing the library + testing app (refs #492)

refs #480