Implement eth-docker backend

[remyroy]

Implement the IMultiClientInstaller interface for the eth-docker backend.

• Initial implementation with preInstall, install, postInstall, stopNodes, startNodes, importKeys
• Harden & tested implementation for all clients for importKeys and startNodes
• switchExecutionClient, switchConsensusClient implementation
• uninstall implementation
• log streaming from eth-docker execution
• better error/exception reporting for UI (wrong password for sudo, issue with preInstall, etc)