Command to delete grids that fail an IsWorking check for a specified block.

[kontu]

Commit 911b610 is just updating my fork to the current TorchAPI/Essentials master.

Commit 6aafed3 adds a "delete offtype" command to "!cleanup" to delete grids based on whether a specified blocktype is non-functional isWorking == false

Code originally written by Teknikal (AdamOckley), he just asked me to put in a clean pull request for it for him.