Add a number of tests for the dev-tools. The tests iterate over all .xls files that are found under test-data, any newly added file or code-change which breaks one of the dev-tools will cause the tests to fail in the future. Known broken files can be excluded. Also fixes two points where some files could cause BiffViewer to fail.
poi/trunk/src/java/org/apache/poi/hssf/dev/BiffDrawingToXml.java
poi/trunk/src/testcases/org/apache/poi/hssf/dev/