Generate test_client yaml from within the WBEMConnection operation methods

[andy-maier]

In order to produce more test_client yaml testcases, it would be beneficial to generate those, instead of making them up manually. This can be achieved by having code in the WBEMConnection class in imethodcall() and methodcall() at the end when the result is available, that emits the yaml testcase for this operation. At this point, everything is available: Python input and output, and CIM-XML request and response (via debug). This could be controlled by another WBEMConnection instance attribute.

[andy-maier]

Would like to wait with this until PR #320 has been merged.

[andy-maier]

PR #320 has been merged; started working on this one.

[andy-maier]

PR #366 is an initial stab at an operation recorder, but its TestClientRecorder only displays the operation, and needs to be implemented for writing a test_client testcase.

[andy-maier]

PR #384 is the next step. Its TestClientRecorder supports operation args and results, but still has some limitations (see the PR for details).

[andy-maier]

PR #384 has been updated and is now the complete implementation.