pnpm 5.2.3 on Node.js NPM

Own implementation of the pnpm bin command added (previously it was passed through to npm bin).
Read the correct PATH env variable on all systems, when running pnpx. One Windows the correct path name might be Path or other.
Install the pnpm bin executable to the directory of the globally installed pnpm executable, when running pnpm add -g pnpm.
pnpm store prune should not fail when the store has some foreign files.
pnpm unlink --global should unlink bin files from the global executables directory.