* Improved completion support for files with spaces

Filenames with spaces, both generally and for session names, will now
complete as expected.

* Misc shell script improvements

See discussion on:
1cca9e4b72

1. getplugs should work even if nnn is not run
2. Remove redundant ./ prefix
3. Update plugin docs

* Implement plugins control of nnn + plugins

* Refactor plugins control code and fix getplugs to recognize hidden files

* Fix bug when going to dir on non-current context from plugin

* Fix some plugins to work on openbsd and freebsd

* Renamings

* Switch to -R flag in cp instead of -r; BSDs complain

* Change braces of function location

* Rewrite plugin creation in README and add new plugins to the table

* Update the fzcd script to include fzy or fzf

* Change plugin name resolve-link-dir -> lncd

* Fixing plugins README table

* Remove some cd plugins but add them as examples to plugins README