Add a plugin for determining disk usage as a subcommand to fs.
Allow sorting of args to be set, default is sorted.
Don't sort arguments for 'fs usage'.
Fix flake8 errors introduced cut and paste.
Rename usage helper methods.
Allow no args and have that return current user's usage.
Add groups option to show usage of user's groups.
Add a docstring for usage.
Merge pull request #3009 from ximenesuk/disk-usage-plugin-plus

Add a disk usage plugin