enable statictics on how often each procedure was executed/digest was computed

[Franziska-Mueller]

In the web UI it would be great to show statistics for each SC, how many times each procedure was called and how often the state digest was computed.

• check which procedures are already covered by log messages
• for END_TICK and BEGIN_TICK, we can probably just assume that they run every tick
• we need to add a log message for state digest computation