Support MDF output and always write to DAQ/RawEvent

• Add functionality to write MDF from HLT2, closing #228 (closed)
• Always write in "0.x" format by combining raw event parts into DAQ/RawEvent
• Remove bank killing (as the output raw event is assembled from parts), closes #264 (closed)
• Write DecReports with the correct SourceID, closes #241 (closed)

Goes together with LHCb!2978 (merged) and MooreAnalysis!32 (merged)