Add (more) line numbers to code examples in Zend Studio tutorial
Update headline structure for Zend\Captcha

Another small step for a consistent structure.
Merge remote-tracking branch 'origin/pr/1254'

Close #1254
Merge remote-tracking branch 'origin/pr/1255' into hotfix/1255
[#1255] restore case in heading
Merge branch 'hotfix/1255'

Close #1255
[2.3.1] bumped release version
Merge branch 'releases/2.3.1'

2.3.1 release readiness
Version bump: 2.3.2dev
Merge branch 'version/bump'

2.3.2dev