README for "src/userguide"

Explains the contents of the directory and shows how to run the examples.
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+This directory contains source code that is not part of the Apache
+Commons Math library.  It contains syntaxically correct and working
+examples of use.
+
+In order to run one of the applications (a class that must contain a
+"main" method), you would type (in a shell console) a command similar
+to the following:
+ $ mvn -q exec:java -Dexec.mainClass=org.apache.commons.math3.userguide.sofm.ChineseRingsClassifier