Add worldedit Pattern commands

## Describe your suggestion
Add worldedit pattern commands. For example:
//set stone,diorite,andesite,granite
//set 50%red_wool,10%red_stained_glass

Cause now it can only place one sort of block with: sel fill [block] or sel set [block]

## Final checklist
- [x] I know how to properly use check boxes

Start by locating the handlers for the existing `sel fill [block]` and `sel set [block]` commands referenced in the issue. Read how they parse a single block and apply it, then define support for the listed block lists and percentage patterns; done means both example forms place the requested distribution of blocks.

Written by the indexing model from the issue text.