Clean up import order.

Add a key ('F') and a command line option (--fs-free-space) to display FS free space instead of used space (issue #411)

Add a tag --process-short-name to force display of processes short name instead of full path (issue #407)

One-line docstring should not occupy 3 lines
Expected 1 blank line *before* class docstring
First line should end with '.'
Blank line missing between one-line summary and description
No blank lines allowed *after* method docstring
Use r""" if any backslashes in a docstring

Use CapWords convention for class names
Use new-style classes
Use lowercase with underscore for function and local variable names
(to be continued)

Use format() instead of % method.

-v is for verbose.

- remove obsolete code
- glances_password: update comments and fix typos
- re-apply fix to avoid string format conflicts (screwed up after
  feature branch merges)
- strip trailing whitespaces
- flake8

To be continued...

Explicit is better than implicit.