Support a whitelist of option names to include in notifications

[plambert]

As a way to address https://github.com/rundeck-plugins/jira-notification/issues/7 we should add a text configuration field that accepts a list of options to include in the notification.

If this is left empty (the default) then all options are included in the notification text; if it is a comma separated list of options, only those in the are included in the notification text.

If an option is included in this list which doesn't exist in the actual context, we should specifically call that out in the notification. For example:

Warning: These options were specified in the Rundeck JIRA Notification Plugin for inclusion, but are not actually defined in the context of this job: option-one, another-option, ...

[gschueler]

I believe that the context data (used to iterate the "option" entries) will also contain "secureOption" entries, which could be used to exclude any password field values.