Suggestion: loadFixtures(): Change the default for append to false

[ThomasLandauer]

The default mode when loading fixtures is to purge: https://symfony.com/bundles/DoctrineFixturesBundle/current/index.html#loading-fixtures

By default the load command purges the database

But with $I->loadFixtures(), the default is to append. I think this is confusing and should be changed. However, I don't see any easy upgrade path... ;-)