Graceful handling when dpfile parameter is missing in cid2xml

[Jackkal]

This PR adds a graceful handling when the dpfile is not given as argument in cid2xml, but a dp resource is expected by the cid class. The dpfile argument is optional since not all cid classes require a dp resource, but the cid2xml core dumped when a dp resource was expected by the specific cid class, but not given as argument to cid2xml.

Before: $cid2xml cid_taskdefinition.bin Segmentation fault (core dumped)

After: $cid2xml cid_taskdefinition.bin Error: /code/OpenAWE/src/awe/objectbinaryreadstream.cpp:36: dp file expected but not defined