Release Metafacture core 6.1.2

[dr0i]

This release fixes a bug introduced in 6.1.1 #546.

All new features since 6.0.0 will be documented in 6.1.2.

• update dependencies if these are promising to not break much
• (as this is a quick-bug fix release only affecting MARC-XML producing programs there is no real test release candidate. Playground and oersi test were successfully done.)
• release on maven central
• release on github
• release metafacture-fix 1.1.2
• release metafacture-playground 1.1.2
• update flux-commands
• copy metafacture-fix' functions-and-cookbook to https://github.com/metafacture/metafacture-documentation/blob/master/docs/fix/Fix-functions-and-Cookbook.md
• write blog post, see PR
• toot
• write to email list
• announce at metadaten.community

[dr0i]

All done here. Closing.