sublime: refactor plugin and fix documentation (#7715)

* convert to 2-space indentation
* standardize sublime function name (subl)
* simplify subl function definition into a single loop
* convert functions into aliases
* simplify alias creation
* search for Sublime Text command only if not found
* reorganize and clean up plugin
* fix README
* simplify cygwin path lookup
* support path lookup for msys (Windows)
* support path lookup for WSL (Windows)
* fix for spaces in sublime path alias