Update salt-key manpage to reflect changes to "-l" arg
Update salt-key CLI help

This rewords the help for "salt-key -l". This same wording was used to
update the manpage in f2b036b
Update rst docs to reflect rename to salt/modules/localemod.py

This updates the rst docs to match the change made in ef90d58.
Remove old locale module rst file
Merge pull request #5433 from terminalmage/issue4094

salt-key documentation updates