Referencing removed Apache POI classes preventing Apache POI upgrade

[heiching]

Removed classes referenced:
org.apache.poi.utils.SAXHelper
org.apache.poi.hssf.util.CellReference

SAXHelper:

zerocell/core/src/main/java/com/creditdatamw/zerocell/ReaderUtil.java

Line 10 in 69b02d0

import org.apache.poi.util.SAXHelper;

CellReference:

zerocell/processor/src/main/java/com/creditdatamw/zerocell/processor/spec/CellMethodSpec.java

Line 51 in 62a6547

.addStatement("int column = new $T(cellReference).getCol()", org.apache.poi.hssf.util.CellReference.class)

org.apache.poi.utils.SAXHelper is used in ReaderUtil and prevents Apache POI to be upgraded beyond 3.
SAXHelper is refactored in Apache POI 4.x to org.apache.poi.ooxml.util.SAXHelper and further removed in POI 5.0.
Apache POI suggests to use org/apache/poi/util/XMLHelper instead.

org.apache.poi.hssf.util.CellReference is refactored to org.apache.poi.ss.util.CellReference

Apache POI deprecation info: https://poi.apache.org/apidocs/dev/deprecated-list.html#class