Metabase 0.18.1

Patch release to fix some bugs that popped up.

Enchancements

#2812 - Add documentation on how to upgrade your Metabase instance

Bug Fixes

#2829 - Hour of Day is being sorted incorrectly in line charts
#2823 - Foreign key fields appearing as "field" in FieldName widget
#2821 - Column Ordering
#2819 - Hour-of-day line charts ordered incorrectly
#2732 - Native queries for Mongo and visualisation