Simplify peer selection before login

[karmacoma]

Expected behaviour

Provide the user with 3 options.

1. Mainnet (Random peer from network) <- The default option
2. Testnet (Random peer from network)
3. Manual (Defaulting to localhost:8000)

The manual option would allow the user to specify any: hostname and port they desire. It could be presented as a modal.

Actual behaviour

A selection of peers is presented to the user like so:

Steps to reproduce

Open lisk-nano and click on Choose a peer.