Ongoing work on H**F to support passing password as a param

[pjfanning]

Some work merged to trunk branch already.
Main issue is that legacy needs you to set the password on a ThreadLocal. Biff8EncryptionKey static methods.
Relates to #1015
Remaining:

• HSLF read
• HSLF write
• HWPF write
• EventBasedExcelExtractor