DDNS Forward/Reverse updates (#11)

* Copy kea semantics for ddns update (squash)

initial ddns

update ddns options

crate dhcid

start forward update

fix ddns test

ddns: construct ddns update Message

ddns: no more of forward update

ddns: move to update module

ddns: add reverse update

ddns: set hostname in fqdn response

ddns: trigger update in leases plugin

ddns: select forward/reverse based on longest match

ddns: prereq ttl=0 & add port to dns server

update dhcproto

* fix test

* add ddns docs

.gitignore

@@ -1,5 +1,6 @@
 out/
 data/
 target/
+data/
 *.db*
 .vscode/*.log