Merge pull request ethereum#4022 from ethereum/develop

`develop` changes into `master`

Layered nodes

Merge pull request ethereum#3766 from ethereum/artifact-uploads

Refactoring upload-queue task; Prettier code style changes

Ethereum Wallet and Mist v0.9.3

- Electron update to 1.7.8

- Light client integration

Mist and Ethereum Wallet update

Ethereum Wallet and Mist update

Ethereum Wallet and Mist 0.8.9 - "The Wizard"

Release 0.8.8