korapxml2conllu: add option --colmuns=<n>

Print only n columns and only the token if n=1. Mainly useful to pass data
tools that are not CoNLL-U-ready.

Change-Id: I078093b2484cc9ef9eb40b87c63ec3784d8eae38
diff --git a/Changes b/Changes
index d5acfb1..b250585 100644
--- a/Changes
+++ b/Changes
@@ -1,4 +1,5 @@
         - korapxml2conllu: use morpho.xml if present when run on base zips
+        - korapxml2conllu: new option -c <columns>
 
 0.4.1 2021-07-31
         - korapxml2conllu: fix patterns not extracted for last texts in archive