Using as_xml for barcode recognition

Added opportunity to recognize barcodes with `barcode_image.as_xml([:english], :barcode_recognition)`.

Example of the XML's response:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <document xmlns="http://www.abbyy.com/FineReader_xml/FineReader10-schema-v1.xml" version="1.0" producer="ABBYY FineReader Engine 11" languages="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.abbyy.com/FineReader_xml/FineReader10-schema-v1.xml http://www.abbyy.com/FineReader_xml/FineReader10-schema-v1.xml">
    <page width="2400" height="3200" resolution="290" originalCoords="1">
    <block blockType="Barcode" blockName="" l="615" t="1711" r="1387" b="2138"><region><rect l="615" t="1711" r="1387" b="2138"/></region>
    <text>
    <par><line baseline="0" l="0" t="0" r="0" b="0"><formatting lang="">46143761</formatting></line></par>
    </text>
    </block>
    </page>
    </document>