Add option to complete final phase of pt-osc and rename table

https://blueprints.launchpad.net/percona-toolkit/+spec/pt-osc-no-drop-triggers recognised some users want to delay changes to coincide with low load or to coincide a database change with an application release.

With https://blueprints.launchpad.net/percona-toolkit/+spec/pt-osc-no-drop-triggers now implemented, the options --no-swap-tables --no-drop-new-table --no-drop-triggers can be used to make a change whilst delaying the rename tables operation. It would be useful to implement a --rename-table option to abstract the manual rename table operation required to swap the existing table with the new table.

Ideally this new option should complete Steps 5-7, and should be compatible with the --alter-foreign-keys-method option to ensure an appropriate strategy can be selected.