[poi]excel导出，增加动态列支持

[wayshall]

excel导出，增加动态列支持

[wayshall]

field元素增加iterator属性，支持通过集合动态创建列

<?xml version="1.0" encoding="UTF-8"?>
<template name="报名客户资料">
    <rows>
        <row span="2" fieldStyle="alignment:ALIGN_CENTER;verticalAlignment:VERTICAL_CENTER;" fieldFont="boldweight:BOLDWEIGHT_BOLD">
            <fields>
                <field value="'报名客户资料'" rowspan="2" colspan="3+#dynamicCellHeaderList.size"/>
            </fields>
        </row>
        <row name="element" renderHeader="true" type="iterator" datasource="#cardList" fieldFont="boldweight:BOLDWEIGHT_BOLD"> 
            <fields>
                <field name="id" label="主键" />
                <field name="cardNo" value="cardNo+'--for--test--'+cardPwd" label="卡号"/>
                <field name="cardPwd" label="密码"/>
                <field name="header" label="#header.name" value="#element.dynamicProperties[#header.id]" iterator="#dynamicCellHeaderList"/>
            </fields>
        </row>
    </rows>
</template>