Fix conflicting inset font defaults (bug #8874)

Fix conflicting inset font defaults (bug #8874)

This makes the defaults of Inset::inheritFont() and Inset::resetFontEdit()
compatible. There is no user visible change except for the Chunk inset which
does not produce invalid LaTeX after editing operations anymore.
This is the safe version for 2.1.0, for later there are still open questions:
- All insets with ResetsFont true should be audited: Is this really needed,
  or do they show similar editing problems as the Chunk inset?
- Does inheritFont() need to be customizable in the layout file as well?
- Is resetFontEdit() != !inheritFont() needed at all?
I did not use change tracking for the docs, since I updated all existing
translations.