Certificate Authority Module

This release adds support for the latest version of icingaweb2

• In recent icingaweb2 versions the system menu is now a submenu. As a consequence, the CA menu won't show up. Fix that
• Report error if ca list command failed

Thank you @araujorm !!

Fixes https://github.com/nunofernandes/icingaweb2-module-ca/issues/6

In the previous release I forgot to update the version information. This fixes that (only cosmetics).