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)
  • Future DNS Documentation options #77
• listen.host can contain a hostname
• Document lighthouse.advertise_addrs #46
• Explore documenting undocumented config options #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