#745298 by moshe weitzman. FieldHandler prepare functions take the  (passed through in MigrateFieldsEntityHandler->prepare)

Refactor the example fetch callback so that it uses a new helper function. See migrate_execute_sql() ... Also some drush validate fixes.

A different direction. This one starts fresh with migrate as a drush based application. Its only web component will be a read-only dashboard. All content sets and their fetching callbacks are defined in code. See migrate_example module as an example. Still lots of work to do. Don't bother running this yet.

#679216, #678378 by frankcarey, mikeryan: Implement hook_migrate_api() and move contrib module support to migrate_extras

#661934 by frankcarey, mikeryan: Support for external tables using views/tw dbname.tablename support