* doc: cleanup and key-value for optional parameters
* rebalance: cleanup and refinements
* sendinvoiceless: cleanup and refinements
* summary: reflects upcoming changes of pylightning to_approx_str
* rebalance: check peer connection on local channels
- sends payment without an invoice from the receiving node
- uses circular payments: takes the money to the target node, pays in the form of routing fee, and brings some change back
- no plugin/update required on the receiving side