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)