Cleanup the handling of default anonymization parameters

[pdobacz]

This is a follow-up to this discussion.

Right now the defaults are somewhat dispersed and inconsistent. After the dust settles on DfD releases and UI, let's rethink the approach on which components are responsible for defaults and make things consistent

Currently the defaults (and also documentation on recommended values) live in:

• desktop (most likely the most recent version of defaults)
• reference
• pg_diffix
• papers and docs