Support `$_Z_DATA` environment variable per z's documentation dcd5541e7d/z.1 (L78).
`$_Z_DATA` allows changing the default location of the z database file.
* Added fzfz plugin
* Fixed shellcheck errors
* Fixed copy/paste error
* Added support for fzy, also renamed plugin since it's not specific to fzf anymore
* Refactored code
* Clean spillovers (jarun)