Fix missing history.xml bug

This release offers a new property Reader.mff_flavor similar to existing Reader.flavor that doesn't rely on the presence of "history.xml" nor its content. Instead a file is recognized as 'segmented' if "categories.xml" is present, and as 'continuous' otherwise. The existing API is deprecated.

Added

• dependency Deprecated

Changed

• deprecate property Reader.flavor in favor of Reader.mff_flavor