Refactor debug stream handling in TrigTransform

Refactor debug stream handling in TrigTransform:

• retrieve Atlas Project name from DB
• move to ROOT 6
• move to cppyy 1.6.1
• whitespace changes to unify touched parts of files
• handle athena --use-database flag (no longer supports value)
• check if BS file for post processing exists
• remove --debug_stream' argument and instead rely on outputHIST_DEBUGSTREAMMONFile

Tagging @mark