Port to DNSJava 3.5.1, Java 8, linter fixes (#13)

* Initial port to dnsjava 3.5.1

* java.util.Date -> java.time.Instant
* for (Iterator ..) to for ( Object : List )
* DSRecord.<digest type> -> DNSSEC.Digest.<type>
* source to java 8

* formatting overhaul; copyright; author

* add slf4j jars for dnsjava 3.5.1

* NSEC/NSEC3 ttls are now min(soa.min, soa.ttl)

* Upgrade to commons-cli-1.5; some linter fixes

* Add CDS support of jdnssec-dstool

* linter suggestions

* add a TODO list

* Add a TODO list

.gitignore

@@ -1,4 +1,5 @@
 build
+bin/main
 .classpath
 .project
 .gradle
@@ -6,4 +7,4 @@ jdnssec-tools*.tar.gz
 docs
 test-zones
 settings.json
-.settings
+.settings