Allow truncating the logs

[Vladimir Kalnitsky]

Currently, we have a suppressLogs option, that allows to hide logs from successful contract executions. But in case there is an error, we see everything, which is not convenient (it's usually low thousands of log lines). We need to be able to truncate the logs and only print last N lines, saving everything to a file.

[Joseph Young]

Maybe this should be a separate request, but I've also wanted to be able to suppress logs beyond a certain log level, so, for example:

• INFO/ERROR/WARN level logs get logged immediately
• Upon failure, all other logs (eg TRACE) are displayed, but also include the immediately logged