Upload to handle ptf_variable.id field to allow clean matching

[tomlatter]

Current rule in parser (pre-save), for SOT theme:
if existing UNCLOSED PTF_VARIABLE MEASURING SAME VARIABLE (existing ptf_variable with end_date is null)
then:

1. IF DIFFERENT SENSOR MODEL OR SAME MODEL BUT SERIALS DIFFERENT -> AUTO-CLOSE PREVIOUS AND ADD NEW (CLOSES EXISTING PTF_VARIABLE ON THE NEW START_DATE OR CURRENT_DATE IF NO START_DATE PROVIDED)
2. IF SAME MODEL WITH SAME SERIALS OR BOTH SERIALS NOT PROVIDED -> UPDATE PREVIOUS, DON'T ADD NEW (CANCELS ADDING NEW PTF_VARIABLE AND INSTEAD UPDATE EXISTING WITH ANY VALUES THAT ARE CURRENTLY EMPTY - DOESN'T UPDATE WIH NULL VALUES)

Proposal, same rules for all networks, no automatic deleting or closing:

• remove all automatic closing
• include a new 1-2 character short_code for each sensor setup, unique within ptf
• allow operators to generate this short_code if they are creating new sensor setup
• for updates of sensor setups, operators need to provide id or shortCode of the sensor setup
• matching only done on id or shortCode
• do not automatically delete existing ptf_variables, and potentially never delete