Remove duplication of plate creation date info in db #449
Description
#412 introduced a new creation_timestamp column into the labman.plate table. Technically, this is a duplication of data: plate creation dates are already stored in the db as the run_date of the process that created the plate. If we ever have time, we may want to clean this up.
Note this is the same sort of issue as that described in #220 : convenience fields in db cause data duplication and thus the potential for multiple (different) values where there should only be one.