Repeated checks can be replaced by modifier

[ryu9827]

Checks for contract owner and user existence are repeated for many times in different functions in ProofOfPhysicalAddress.sol. Suggest to use a modifier to replace repeated codes.
Check for contract owner :
Line61, Line66, Line74, Line83

Check for user existence:
Line97, Line111, Line129, Line147, Line161, Line169, Line204, Line221, Line293, Line325