Ensure we can control the log level
Provide Munin::Common::Logger::configure
Set default screen log level to "critical"
Handle --debug and --screen options for log level and output
Silence logging during tests
Ensure that switching between log outputs works as intended
Use options --screen and --debug
Update documentation with --screen and --debug
Merge pull request #241 from ssm/feature/log-level

Ensure --screen and --debug works for munin-update, limits, html, graph