Issue #2260239 by ultimike: D6->D8 Profile field (checkbox).

...migrate.migration.d6_user_profile_entity_form_display.yml

...onfig/install/migrate.migration.d6_user_profile_field.yml

...al/migrate_drupal/Tests/Dump/Drupal6UserProfileFields.php

...upal/migrate_drupal/Tests/d6/MigrateProfileValuesTest.php

...e_drupal/Tests/d6/MigrateUserProfileEntityDisplayTest.php

...upal/Tests/d6/MigrateUserProfileEntityFormDisplayTest.php

...e_drupal/Tests/d6/MigrateUserProfileFieldInstanceTest.php

...l/migrate_drupal/Tests/d6/MigrateUserProfileFieldTest.php