Allow to duplicate a plan to a new plan

As a MTV user, I want to be able to clone a plan to a new plan, in order to be able to quickly create new plans with the same parameters (mappings, hooks...).

When the new plan is created, the list of VMs is also duplicated, to allow migrating the same VMs to a different namespace.

Also this is added, to improve the user experiance when a cancelled/failed plan needs to be edited:

Bug 2011805 - [MTV UI] Add a tooltip suggesting using duplicate plan for failed/cancelled migration plans
https://bugzilla.redhat.com/show_bug.cgi?id=2011805