Integrate "migration" page to IPA Web framework.
To use all advantages of entire Web framework the "migration" page
should use "migrate" plugin. As well this allows to use IPA
translations.
Fixes: https://pagure.io/freeipa/issue/7641
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
Reviewed-By: Serhii Tsymbaliuk <stsymbal@redhat.com>