[oozie] Support Pipe action

    <xs:complexType name="MAP-REDUCE">
        <xs:sequence>
            <xs:element name="job-tracker" type="xs:string" minOccurs="1" maxOccurs="1"/>
            <xs:element name="name-node" type="xs:string" minOccurs="1" maxOccurs="1"/>
            <xs:element name="prepare" type="workflow:PREPARE" minOccurs="0" maxOccurs="1"/>
            <xs:choice minOccurs="0" maxOccurs="1">
                <xs:element name="streaming" type="workflow:STREAMING" minOccurs="0" maxOccurs="1"/>
                <xs:element name="pipes" type="workflow:PIPES" minOccurs="0" maxOccurs="1"/>
            </xs:choice>
            <xs:element name="job-xml" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="configuration" type="workflow:CONFIGURATION" minOccurs="0" maxOccurs="1"/>
            <xs:element name="file" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="archive" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
        </xs:sequence>
    </xs:complexType>

    <xs:complexType name="PIPES">
        <xs:sequence>
            <xs:element name="map" type="xs:string" minOccurs="0" maxOccurs="1"/>
            <xs:element name="reduce" type="xs:string" minOccurs="0" maxOccurs="1"/>
            <xs:element name="inputformat" type="xs:string" minOccurs="0" maxOccurs="1"/>
            <xs:element name="partitioner" type="xs:string" minOccurs="0" maxOccurs="1"/>
            <xs:element name="writer" type="xs:string" minOccurs="0" maxOccurs="1"/>
            <xs:element name="program" type="xs:string" minOccurs="0" maxOccurs="1"/>
        </xs:sequence>
    </xs:complexType>