Prepare for gec-appender-logback by moving log4j module to gec-appender-log4j
Basic logback appender
Merge branch 'master' into logback-support
Version updates
Tweak names
Rename appender classes to GecLog4jAppender and GecLogbackAppender, respectively
Add a note about GecContext being duplicated
Fix stack trace filtering after renaming
Update doc