Implement test 6.1.34

[oxisto]

https://github.com/oasis-tcs/csaf/blob/master/csaf_2.1/prose/share/csaf-v2.1-draft.md#mandatory-tests--branches-recursion-depth

[tschmidtb51]

This test seem to be implemented. However, A quick check with the available test files show, that there seems to be a bug in here as it fails on a valid test file with 30 consecutive nested branches.

This is related to #23

[milux]

The check contained a condition that failed if "depth < 30", which should have been "<= 30". This should be fixed by #25 as well.