Add migration for contact_save

Here is a work-in-progress patch. I have not been able to start testing and debugging what else needs to be done because even though migration template is in config it's not being picked up by migrate-upgrade --configure-only.

This patch successfully migrates data one time. It looks like it migrates in dupes if run each consecutive time.

This interdiff looks a bit weird but that's what interdiff output. :|

todo:

1. Recipients process plugin
2. Add created date to migration
3. UID migration

for discussion:

- should this also migrate and create fields for reply, replied, replier, and uid?

Also, switching from SourcePluginBase to SqlBase caused a dependency on adding 'migrate' key into databases in settings.php. I'm not sure why.

This should be feature complete for Drupal 6 migration of contact_save with the addition of created and recipient migration.

If another module has changed the cardinality of the recipient field to multiple values, then this migration will support that. However, if not, then it will just use one recipient.

Re-rolled patch based on git pull.

Edit: any additional features could be added by another module or for Drupal 7 contact_save.

Migrate tests are not my strength so let's see how much this patch fails.

Edit: this is just a start of a test.

Hmm.. Maybe test_dependencies?

Oh, it was removed some time in 8.1.x development but no change record exists for it? :(

Found you sneaky issue #2684141: Convert migrate kernel tests to KernelTestBaseTNG.

Anyway, here's a patch that should at least run in 8.2.x.

Another try.

Fixed namespace

Install schema before test similar to other kernel test.