ability to set "Trigger for matrix projects" global default

[jhoblitt]

Multi-cofiguration job types have a additional "Trigger for matrix projects" configuration parameter not present in freestyle jobs. This parameter is not exposed in the global plugin configuration and has to be set on a per job basis. It would be very convenient to be able to set a global default for this value.

[aldaris]

In my opinion the settings for this plugin are already overcomplicated. Most likely I will only look into this request if it gets ~10 thumbsups.