Issue #64 - Add javadoc and README

Author: boretti

README.md

@@ -161,6 +161,13 @@ Also, some dedicated, _ready to used_, Exception Mapper are provided :
 * `saxExceptionMapper()` - Return an exception mapper that adds to the message of the `RuntimeException` the SAX Error from the underlying exception. **This is only usable when the module java.xml is available**.
 * `transformerExceptionMapper()` - Return an exception mapper that adds to the message of the `RuntimeException` the Transformer Error from the underlying exception. **This is only usable when the module java.xml is available**.
 
+### CommonsCollections4Helper
+
+_This helper is only available since version 2.2.0 and only if the commons-collections4 library is available_
+
+The class `CommonsCollections4Helper` provides several static methods to convert interface
+from this library to the corresponding version in commons-collections4.
+
 ## Reference
 
 The following classes are provided:

src/main/java/ch/powerunit/extensions/exceptions/CommonsCollections4Helper.java

@@ -37,6 +37,16 @@
  * "https://commons.apache.org/proper/commons-collections">commons-collections4</a>.
  * <p>
  * <b>This class is only available if commons-collections4 is available</b>
+ * <p>
+ * The mapping between the interface from <i>commons-collections4</i> and this library is the following :
+ * 
+ * <table border="1" summary="Mapping between interfaces">
+ * <tr><th>commons-collections4</th><th>powerunit-extensions-exceptions</th></tr>
+ * <tr><td>Predicate</td><td>PredicateWithException</td></tr>
+ * <tr><td>Factory</td><td>SupplierWithException</td></tr>
+ * <tr><td>Transformer</td><td>FunctionWithException</td></tr>
+ * <tr><td>Closure</td><td>ConsumerWithException</td></tr>
+ * </table>
  * 
  * @since 2.2.0
  *