Poi bug 61528,61349, 60737, 59747

[antony-liu]

Main changes:

• Bug 61528 - Pivot Table enhancements, new example [Thanks to R Kietel]. This closes some excel functions #71
• Bug 61349 -- add more sanity checks when allocating byte[]
• Bug 59747: Adjust order of first two entries in the resulting Zip to try to enable some external tools to auto-detect the file-type
• Apply patch to add endSheet() to the XSSFEventBasedExcelExtractor, fixes bug 60737, thanks to user zakim for the patch