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

licenses/slf4j-LICENSE.txt

@@ -0,0 +1,21 @@
+ Copyright (c) 2004-2017 QOS.ch
+ All rights reserved.
+
+ Permission is hereby granted, free  of charge, to any person obtaining
+ a  copy  of this  software  and  associated  documentation files  (the
+ "Software"), to  deal in  the Software without  restriction, including
+ without limitation  the rights to  use, copy, modify,  merge, publish,
+ distribute,  sublicense, and/or sell  copies of  the Software,  and to
+ permit persons to whom the Software  is furnished to do so, subject to
+ the following conditions:
+ 
+ The  above  copyright  notice  and  this permission  notice  shall  be
+ included in all copies or substantial portions of the Software.
+ 
+ THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
+ EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
+ MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
+ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
+ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.