bash-completion: Invoke actual commands to be completed, not basenames

Addresses partially: http://bugs.debian.org/769462
Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
docs: Spelling fixes

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
Signed-off-by: Karel Zak <kzak@redhat.com>