Elevation ranges are not parsed

[jocelynpender]

Elevation ranges are not parsed into max and min of range. This would be great to have.

See the following from V19_357.xml of the FNA

 <description type="elevation">
    <statement id="elevation_0">
      <text>10–1000 m;</text>
      <biological_entity id="elev_o0" name="whole_organism" name_original="" type="structure">
        <character name="elevation" value="10–1000 m" />
      </biological_entity>
    </statement>
  </description>