[input-output-hk/cardano-sl] [CBR-97] structured logging (#3401)

* rebased on current `develop`
some changes were needed in ‘util’ because of `RecordWildCard` — I have mentionned the fields explicitely when the structure is not locally defined
* removed the change to turn off optimisations in `wallet/src/Pos/Wallet/Web/Server/Handlers.hs` -> expect Appveyor to fail