AIP - 86 (bis): Swap EURC to ERNX

This is an extension of this [vote of the EURC to ERNX swap](https://snapshot.org/#/anglegovernance.eth/proposal/0xfe921b3193f9ed342d87e64dfb83c2dc42001cac41720cbc491d8cda6d833a09) to clarify and validate with the DAO some elements which were not fully specified in the first implementation of the vote. In particular, the vote mentioned a change in the oracle methodology for the Transmuter. Here is the fully tested and reviewed PR with the proposed changes:...