Return number of affected rows after deleting.
Do not load before saving.

- Allow implementing modules that use exportable tables to use hook_schema() (and thus change management via hook_update_N) on data managed tables.
- Make CTools a hard dependency. It has been a matter-of-fact dependency before, requiring it simplifies code.
- Add a .install to data_ui_test module: required for simpletest to set up and break down cleanly.

All tests passing. However, there remains a problem with occasionally illegal table definitions generated by fields generator in data_ui.test.

Only create field if random values yield result, throw error when random value source array is empty.