Include geth update and start logic into shell

[PhilippLgh]

This is a rewrite of the geth binary download, start, stop and configuration logic.

Related to

• https://github.com/ethereumjs/geth.js
• https://github.com/ethereum/ethereum-client-binaries
• https://github.com/ethereum/mist/blob/develop/modules/clientBinaryManager.js

Requirements analysis based on Mist issues:

• attach to an already running geth node: Mist doesn't attach to already running geth instance mist#3859
  -> many users just chose this way because they cannot make fine-grained configurations about e.g. the datadir in the UI. If we allow a better config through Mist it will resolve many of the problems that happen because people try to bypass the default config.

• support user IPC configuration: --rpcpath ignored by Mist when connecting to private network mist#3809

• let users explicitly choose their node from all available (local & remote) geth binaries: Wallet does not update geth ==> light sync breaks mist#3855

• remove flag-pass-through: don't forward electron args to sub-processes unless really needed: electron . --rpc /home/xfj/etherum/data/chain/geth.ipc /usr/local/share/.config/yarn/global/node_modules/electron/dist/electron: error while loading shared libraries: libX11-xcb.so.1: cannot open shared object file: No such file or directory mist#4145, Ethereum Wallet 0.11.1 can not connect to private chain mist#4076
  -> defer geth start so that this can be done through UI instead of CLI args

• provide useful debug info if geth binaries cannot be found or are otherwise 'unavailable': Failed to start node Error: Node "geth" binPath is not available. mist#4157, Ethereum node connection error mist#3978

• provide info for a recommended geth version but don't block if it is not used: sanity check should be warning not error: Mist 0.11.1 doesn't work with geth 1.8.13 mist#4064

• provide better guidance on when to use/not to use http IPC but don't crash: Mist RPC Issues mist#3995

• detect datadir & binary path changes and issue warnings

• allow backup and migration of different --datadir locations:
  Installing the Ethereum 0.11.1 wallet to another drive then C problem: you can't backup your accounts anymore mist#4161
  --datadir option not working mist#4164

Notes

We should try to minimize the dependency footprint here as everything runs on main/privileged: no unnecessary 3rd party modules.