Merge pull request #227 from pawal/master

Added requirement for adding DNSSEC checks from issue #97
Merge pull request #228 from pawal/master

Added DNSSEC11, fixes #97
Initial implementation of dnssec11.
Bugfixes.
Doc and translation to English and Swedish.
Unit tests for dnssec11.
Merge pull request #230 from cdybedahl/add-dnssec11

Add dnssec11. Closes #229.
Fixes #184
Merge branch 'fix-issue-184' of https://github.com/mtoma/zonemaster
Content fixes, no major things