Update config docs w/ new v1.70 config options

[jasikpark]

See https://github.com/slackhq/nebula/releases/tag/v1.7.0 for list

• firewall.local_cidr
• unsafe_route.install
• tun.use_system_route_table
• punchy.respond_delay
• lighthouse.calculated_remotes
• firewall.outbound_action: drop
• firewall.inbound_action: drop
• DNS names allowed in static_host_map (aka they will be refreshed now)
  • https://github.com/DefinedNet/nebula-docs/issues/77
• listen.host can contain a hostname
• https://github.com/DefinedNet/nebula-docs/issues/46
• https://github.com/DefinedNet/nebula-docs/issues/49

  
  ### Tasks

• [x] firewall.local_cidr
• [ ] unsafe_route.install
• [x] tun.use_system_route_table
• [x] punch.respond_delay
• [x] lighthouse.calculated_remotes
• [x] firewall.outbound_action: drop
• [x] firewall.outbound_action: drop
• [x] DNS names allowed in static_host_map (aka they will be refreshed now)
• [x] listen.host can contain a hostname
• [ ] https://github.com/DefinedNet/nebula-docs/issues/46
• [ ] https://github.com/DefinedNet/nebula-docs/issues/49