renamed "other" group label for --group-limit to "all others combined" to be more specific.
added new parameter --stacked to histogram plots to switch between stacked/nonstacked bar histograms.
pattern extraction from loglines. can be used to group by "pattern" in mplotqueries.
added tests for pattern extraction. Fixes #129.
Merge branch 'develop' of github.com:rueckstiess/mtools into feature-129-pattern
Merge branch 'develop' of github.com:rueckstiess/mtools into develop
Merge branch 'feature-129-pattern' into develop