Support failure domains

1. Parse command-line arguments
2. Make it a part of JoinRequest
3. Persist it in the raft group
4. Extend topology.rs with a decision making logics.

changed milestone to %Release 0.1 - Demo

added backlog label

assigned to @rosik

added in-progress label and removed backlog label

assigned to @gmoshkin and unassigned @rosik

mentioned in commit a34eb47b

mentioned in commit fa8e98e3

mentioned in merge request !166 (merged)

mentioned in commit 1fcb55c7

mentioned in commit a3a2d5df

mentioned in commit de653000

mentioned in commit 0755c236

closed with merge request !166 (merged)