Issue #2500469 by svendecabooter, phenaproxima: Migration path for Aggregator 7.x

...les/aggregator/migration_templates/d6_aggregator_feed.yml

...les/aggregator/migration_templates/d6_aggregator_item.yml

...les/aggregator/migration_templates/d7_aggregator_feed.yml

...les/aggregator/migration_templates/d7_aggregator_item.yml

...s/aggregator/src/Plugin/migrate/source/AggregatorFeed.php

...s/aggregator/src/Plugin/migrate/source/AggregatorItem.php

...egator/src/Tests/Migrate/d6/MigrateAggregatorFeedTest.php

...egator/src/Tests/Migrate/d6/MigrateAggregatorItemTest.php

...egator/src/Tests/Migrate/d7/MigrateAggregatorFeedTest.php

...egator/src/Tests/Migrate/d7/MigrateAggregatorItemTest.php

...sts/src/Unit/Plugin/migrate/source/AggregatorItemTest.php

.../src/Unit/Plugin/migrate/source/d6/AggregatorFeedTest.php

.../src/Unit/Plugin/migrate/source/d7/AggregatorFeedTest.php

...ules/migrate_drupal/src/Tests/Table/d7/AggregatorFeed.php

...ules/migrate_drupal/src/Tests/Table/d7/AggregatorItem.php