(REF) GenerateData - Use overrideable 'echo'. Use exceptions.

(REF) GenerateData - Use overrideable 'echo'. Use exceptions.

This removes elements of GenerateData which perform direct output to the user. there
are basically two cases:

1. Outputting advisory/status info (e.g. "echo"). This now goes through a method, which
   can be overriden/replaced.

2. Displaying errors from DAO-calls. Now-a-days, DAO-calls can raise their own exceptions,
   so we don't need to sprinkle it without error-outputs.