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
Allow to add serializers through config
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
First commit of Zend\Db\Adapter\Profiler
Fixed an issue on salt check in Apache Password
Zend\Db Fix for #3290
- Zend\Db\Adapter\Platform\Mysql should have wider rage of possible identifiers in fragment quoting
Added the Apache htpasswd support for HTTP Authentication
Zend\Db Fix for #2563
Safewords should be case insensitive
Zend\Db Fix/Feature for #3294
Allow TableIdentifier in joins for cross schema joins
Added check for $e->getCode() return value, fixes Issue #3501: Exception while createing RuntimeException in Pdo Connection class
Zend\Db:
- added Literal object to Zend\Db\Sql and Zend\Db\Sql\Predicate
Merge branch 'fix/3501' of git://github.com/ggarcia24/zf2 into ggarcia24-fix/3501
Zend\Db - coding standards fix
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