Correctly parse empty Subject header

Without this fix parsing an email with an empty subject header "Subject:" fails.

Fatal error: Uncaught exception 'Zend\Mail\Header\Exception\InvalidArgumentException' with message 'Invalid header line for Subject string' in library/Zend/Mail/Header/Subject.php:39
Fix name of plugin referred to in exception message
Fixed escape breakline

the way it was printing:
    //<!--
    Some script in here...    //-->

and now:
    //<!--
    Some script in here...
    //-->
Fixed breakline to script with content

it was printing:
    <script type="text/javascrit">
        some content...</script>

now it is printing:
    <script type="text/javascrit">
        some content...
    </script>

this does not affect when there is no content, it still prints:
    <script type="text/javascrit"></script>
Removed unnecessary space
fix default value with associative params
Added contstructor to suppressfilter
[#3571] wrote test

- Created test that demonstrates empty subject header is correctly
  parsed
Merge branch 'hotfix/3571'

Close #3571
Merge branch 'hotfix/fix-name-of-plugin-referred-to-in-exception-message' of git://github.com/localheinz/zf2 into hotfix/3575
Merge branch 'hotfix/3575'

Close #3575
Merge branch 'master' of git://github.com/wryck7/zf2 into hotfix/3579
Merge branch 'hotfix/3579'

Close #3579
Merge branch 'master' of git://github.com/tommyseus/zf2 into hotfix/3593
Merge branch 'hotfix/3593'

Close #3593
Merge branch 'zf2-suppressfilter' of git://github.com/youngguns-nl/zf2 into hotfix/3594
Merge branch 'hotfix/3594'

Close #3594
Merge branch 'master' of https://github.com/zendframework/zf2