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).

cat_csv: Support overwriting the existing header using a separate header file

cat_csv: If dialect == None, ignore that file because it's empty

cat_csv: Added support for using - to cat stdin

cat_csv: Abort if output stream closed instead of exiting with an IOError

cat_csv: Ignore any duplicated headers instead of requiring each CSV to have a header identical to the first. Rewrote to pass the CSVs through as lines rather than parsing each row. Because the CSVs are not parsed, checked that all CSVs have the same dialect.

Added cat_csv to concatenate two spreadsheets