CLI-driven log levels

[elena-bondareva]

Ref: bootique/bootique#101

[elena-bondareva]

Travis failure root cause: BQ 0.24-SNAPSHOT with changes for bootique/bootique#111 must be published into Nexus.

[andrus]

I am wondering if our initial design of just changing the root log level is not practical after all:

• It will make all loggers not explicitly configured very verbose (e.g. Jetty would print tons of low-level output).
• It does not affect loggers explicitly configured with less verbose log levels at all.

So maybe a better approach would be to create LogbackModuleExtender that would allow passing configuration resource URLs for "normal" and "verbose" modes. By default we'd use "log.level=debug" as a verbose mode config.

[andrus]

Another thought... I suspect many apps may not want verbosity flags to be present at all (to keep their CLI simple). So to make this whole feature optional, maybe we can implement it as a separate module that can be included if needed. It can be called "logback-verbosity" or something.