WIP: Add Rust lightning implementation

[jtimon]

This is far from ready, but feedback always welcomed.

Replaces:

• WIP: Install rust-lightning-bitcoinrpc #63
• WIP: Add support for rust-lightning-bitcoinrpc https://github.com/jtimon/lightning-integration/pull/1

Dependencies:

• [x] Docker: Eclair: Upgrade openjdk from 8 to 11 #79
• [x] Travis: build clients independently https://github.com/cdecker/lightning-integration/pull/77
• [ ] Simpler argman with only strings https://github.com/TheBlueMatt/rust-lightning-bitcoinrpc/pull/10