Integrate digi event building into cbmreco

Event building (comprising digi trigger, digi event building and event selection) is added to cbmreco. For this, a Subchain Eventbuild was introduced. It covers the functionality of CbmTaskTriggerDigi and CbmTaskBuildEvents in the cbmreco_fairrun task-based framework.

Configuration is through the same YAML file that is also used in cbmreco_fairrun (class MainConfig). This is for the time being side-by-side with RecoParams. We have to integrate that more coherently in the future.

Monitoring data are not yet picked up from the Reco class.