0.8.1

Tutorial:

• Add page margin and page size example to the tutorial
• Add an example of FastODSBus

Library:

• Rename WriteUtil to IntegerRepresentationCache because it's a cache.
• Add support for "Tools > Protect Spreadsheet"
• Add validation of the generated files in the examples module.
• Add slash to directory paths in manfest.xml to ensure they are not seen as files.
• Add support for print ranges
• Add support for header rows and columns
• Make XXXUtil methods static
• Add partial cell content validation