add an array of examples to each xml-dictionary definition

The commit https://github.com/lojban/cll/commit/20725facd62939236ee2c6191f7f4b5a608b747e introduced the following structure within <definition> node of the xml dump:

  <examples>
      <example>
          <source>
              coi .djan.
          </source>
          <target language="English">
              <gloss>
               [greetings] John.
              </gloss>
              <translation>
               Hello, John.
                  </translation>
           </target>
      </example>
          <example>
          <source>
              drata mupli
          </source>
          <target language="English">
              <gloss>
               another example
              </gloss>
              <translation>
               Another example.
                  </translation>
           </target>
      </example>
  </examples>

It is necessary to add to the dictionary in the appendix the list of examples for each word once its <example> node is not empty. It could be something like:

<p>coi .djan. — Hello, John.</p>
<p>drata mupli — Another example.</p>

lojban / cll

add an array of examples to each xml-dictionary definition #370