[spike] modified `webapp` example using an rqlite cluster

[shadeofblue]

(or maybe it could be the todo list?)

• would give us a glimpse on possible requirements for dapp-runner's GAOM

the goal is to determine if GAOM is needed to support such setup in dapp-runner

tasks:

• [ ] take the existing yapapi example as the input: https://github.com/golemfactory/yapapi/tree/master/examples/webapp
• [ ] verify what it would take to replace the single DB server with a cluster
• [ ] make any necessary adjustments to the app to support connections on the cluster instead of the single DB server