unique constraints for ecocomDP tables

[mobb]

script should check that a group of fields in each table is unique: observation table:
observation_id, event_id, package_id, sampling_location_id, observation_datetime, taxon_id, variable_name

others tbd. expect the uniq group to be all the ids (except the record_id) up through variable_name (not value or unit). in other words, each row is uniq except for record_id, value, unit

[clnsmth]

I'll integrate this into the validate_ecocomDP function.

[clnsmth]

Done. Checks added to validate_ecocomDP include:

• primary keys
• composite keys
• referential integrity