* a <A href="http://docs.oracle.com/javaee/6/api/javax/servlet/MultipartConfigElement.html">javax.servlet.MultipartConfigElement</a>.
* <p/>
* {@literal multipart.fileSizeThreshold} specifies the size threshold after which files will be written to disk. Default is 0, which means that the file will be written to disk immediately.
* {@literal multipart.location} specifies the directory where files will be stored. The default is "". A common value is to use the system's temporary directory, which can be obtained
* {@literal multipart.maxFileSize} specifies the maximum size permitted for uploaded files. The default is unlimited.
* {@literal multipart.maxRequestSize} specifies the maximum size allowed for {@literal multipart/form-data} requests.
* <p/>
* These properties are ultimately passed through {@link org.springframework.boot.context.embedded.MultipartConfigFactory}
* which means you may specify the values using {@literal long} values or using more readable {@literal String}
* variants that accept {@literal KB} or {@literal MB} suffixes.