Split up rake db:seed and rake db:seeds:fetch

rake db:seeds:fetch can be invoked by hand now, and rake db:seed no
longer automatically calls it. This allows local edits to seeds.sql

When seeding database, do not drop and recreate the local database
according to an online schema - instead keep the existing local
database. This prevents changes from local migrations from being
overwritten when seeding the database
Merge pull request #2071 from bluerogue251/allow_local_changes_to_db_for_seeds

Allow local changes to db seeds