New SIVACOR-parsing report generator needs fixes

[larsvilhuber]

Diagnostics: the ./automations/18_summarize_sivacor.sh fails when a revision is processed, because there is no REPLICATION-PartB.md.

Other issues: the appendix is directly modified in generated/ but that file is re-generated by other scripts.

Steps to solve:

• the script might want to take the template/original-REPLICATION.md as a fallback for the input REPLICATION-PartB.md - it can re-split it, get a blank PartB, and fill that. https://github.com/AEADataEditor/replication-template-development/blob/development/automations/18_summarize_sivacor.sh#L10
• the script should create REPLICATION-PartB-SIVACOR.md in generated/. (currently $output-dir is not used for that file)
• instead of writing to the appendix directly, it should write a piece of the appendix that then gets included when the appendix gets regenerated. The appendix TEMPLATE https://github.com/AEADataEditor/replication-template-development/blob/development/template/REPLICATION_appendix.md should simply have a line at the appropriate location (note: no header! the header should be generated in the sivacor-partb-appendix.md so that it fits with the rest, but does not appear when no SIVACOR is present.

{{ sivacor-partb-appendix.md }}

• Remove duplication - the insertion of the pieces should work off of a template/REPLICATION-PartB-sivacor.md using the same syntax, and use https://github.com/AEADataEditor/replication-template-development/blob/development/tools/replace_placeholders.py . The script also needs to be updated when re-generating the appendix to "blank" the part about {{ sivacor-partb.md }}, for instance, by writing an empty file. This affects https://github.com/AEADataEditor/replication-template-development/blob/development/tools/generate_sivacor_partb.sh#L103