samples.xlsx subject id and was derived conflict to make it impossible to catch certain types of errors or require redundant information

[tgbugs]

File under validation semantics.

In order to validate that a samples file is well formed we cannot use only the subject id column because it means that was derived from can be blank (because we assume that the sample was derived directly from the subject). Therefore was derived from should always be filled in. This makes the subject id column redundant in many cases. So either we keep it as is and accept the redundant information or we remove subject id. In either case was derived from is required for every sample.