Added that you can now disable just the building/breaking of specific blocks if you're allowing to build/break in general. There's 2 new lists in your config.yml where you can add the corresponding materials of your desire.
For Example: If you're adding "GRASS_BLOCK" there, your Guests can break or place dirt but are unable to destroy the default grass block of minecraft.
This Feature is experimental and can change in upcoming updates so keep this in mind and the feedback coming.