Increase VL change for blockplace.fastplace by a factor of 1000.

There had been a divisor of 1000, not sure why exactly.
Harden the command-pre-process handling against fall-back aliases.

These seem not to have been affected beforehand, due to the nature of
the SimpleCommandMap, however we don't want to exclusively rely on
fetching that one successfully.
Partly stitch up command protection.

- Never skip undoing changes. This is necessary to also process commands
that are not registered or that are fall-back aliases.
- Check adding all plugin commands always.
- Check for aliases as well for decision if to match a command.