Etherscan Read Contract for upgradeable contracts

@rstormsf raised the issue that Etherscan in the Read Contract UI for upgradeable contracts should show the implementation address.

An example of what this would ideally look like:
https://etherscan.io/address/0xA5025FABA6E70B84F74e9b1113e5F7F4E7f4859f#readContract

A current proxy contract doesn’t include a Read Contract UI:
https://kovan.etherscan.io/address/0x6280f9fe8ff98cb795976de97ecb394c43938dee#code