Create a generic ReplaceBlockWorker to compliment TransparencyWorker

[tehbeard]

• Should take a map of block -> new block to convert
  • Passing metadata (colour, rotation) should be optional
  • Should pass namespace (minecraft:stone)
• Should follow the same process as TransparencyWorker

[J4Numbers]

Code exists with all the above steps.
Current to-do list for my own benefit which intermingles with LibSchematic.sh:

• Create a flag for replacing blocks within a schematic
• Create a methodology for selecting which blocks are to be replaced with which
• Test that this methodology and this worker actually work