Update for latest icingaweb2

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 !!

Support upcoming icinga2 2.11

Fixes #6

Fix version info

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

Improve CA Parser

This release improves on the CA parser to cope with the new output of the sudo icinga ca command when installing on rhel/centos >= 7.5.

Fixes #4

First version

This is the first version that is running on production on my icinga master server.