- reduce 4 spaces between help columns as it's too wide for handhelds
- support `]` as prompt in nav-as-you-type-mode when filter is empty
- update plugin docs

This plugin is an alternative to the native batch rename interface in
nnn. qmv from renameutils and vidir from moreutils allow to rename
files without fear of replacing existing files.

* 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