moved everything into /trunk/ to create the standard svn layout, for use with tools that require this (eg. git-svn). IMPORTANT: do NOT do an `svn up`. instead, re-use your working copy's existing files with `svn switch` (http://svnbook.red-bean.com/en/1.6/svn.ref.svn.c.switch.html).

added planning/workflow/derived_columns/range_measurements/low-high_vs_midpoint-uncertainty.VegBank.png diagram, generated from a screenshot of the VegBank Data Dictionary (VegBank.vegpath.org/plot#Elevation)