Revert alembic.stamp "revisions" to "revision"

Revert alembic.stamp "revisions" to "revision"

Reverted the name change of the "revisions" argument to
:func:`.command.stamp` to "revision" as apparently applications are
calling upon this argument as a keyword name.  Pull request courtesy
Thomas Bechtold.  Special translations are also added to the command
line interface so that it is still known as "revisions" in the CLI.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Fixes: #601
Closes: #602
Pull-request: https://github.com/sqlalchemy/alembic/pull/602
Pull-request-sha: 4126635e272f82ec53d630bb77c00cb6ff42cec9

Change-Id: I4312954bedc42bb4b76656a70c95b2b7280efae7