Add validation for duplicate SAMPLE_IDs in time timeline

[inodb]

There can't be duplicate SAMPLE_IDs in the Sample Acquisition and Sequencing tracks:

Let's add a check in the python validator to check for this in the timeline files

See:

https://genie.cbioportal.org/patient?studyId=crc_public_genie_bpc&caseId=GENIE-MSK-P-0021194

[charanbhatia]

@inodb can you assign this issue to me?

[inodb]

@charanbhatia feel free to work on it - thanks so much!