Refine logging levels for worker

[pior]

By default

log only when some information is being processed (like a decision task) or a crash occured

• Level WARNING for root
• Level INFO for caravan
• INFO: Received a DecisionTask for this WorkFlow...
• INFO: Completed DecisionTask

verbose --verbose

• Level DEBUG for caravan
• DEBUG: More info about the DecisionTask (new events since last time ?)
• DEBUG: List of all Decisions (with input or not?)

Debug --debug

• Level DEBUG for root (all loggers)