Accept a list of values in property/value

For example, with the benchmark file "Parabolic/HT/SimpleSynthetics/PressureDiffusionTemperatureDiffusionStaggered.prj" instead of a list of values like

<property>
    <name>permeability</name>
    <type>Constant</type>
    <value>1.e-14 0 0 1.e-14</value>
</property>

<property>
          <name>permeability</name>
          <type>Constant</type>
          <value>
            <object[[i]]>1e-14</object[[i]]>
            <object[[i]]>0</object[[i]]>
            <object[[i]]>0</object[[i]]>
            <object[[i]]>1e-14</object[[i]]>
          </value>
        </property>

is written out.