Add "protection_bypass" priv.

The access privilege allows players that have it to bypass protection
on locked doors/trapdoors, chests and bones.

The priv also allows bypassing any minetest.is_protected() check,
including digging nodes and placing them. It is meant for world
moderators to clean up and fix map issues.

Original patch by red-001. Split up and rebased/rewritten by sofar.

This patch requires https://github.com/minetest/minetest/pull/3800