Rejuvenate log levels

[yiming-tang-cs]

We appreciate your previous feedback and it's very helpful! We added Slf4j support and enhanced our tool after that. Here's a reissue of wala#461 with a new version of our tool. Again, we'd appreciate any feedback and are willing to make further changes if you wish to incorporate our PR into your project.

Settings

We have several analysis settings. We can vary these settings and rerun if you desire. The settings we are using in this pull request are:

• Never lower the logging level of logging statements within catch blocks.
• Never lower the logging level of logging statements within if statements.
• Never lower the logging level of logging statements containing certain (important) keywords.
• Never raise the logging level of logging statements without particular keywords in their messages.
• Avoid log wrapping by disregarding logging statements contained in if statements mentioning log levels.
• Consistent log level transformations between overriding methods.

The greatest number of commits from HEAD evaluated: 1000.
The head at the time of analysis was: b73a0b2