Merge (really a copy/fast-forward) Bard's commits from
git@github.com:10gen/mms-automation.git/go_planner/src/com.tengen/cm/util/slogger.go
commit 14f4b118b15616d2594d8497655cc22eb4a11229

This adds the ability to ignore certain filenames when logging the
caller (works well when building a logging system on top of slogger)

Also adds ROUTINE and DOOM log levels.