Constructor PostingsFormat

Creates a new postings format.

The provided name will be written into the index segment in some configurations (such as when using PerFieldPostingsFormat): in such configurations, for the segment to be read this class should be registered by subclassing DefaultPostingsFormatFactory and calling in the class constructor. The new IPostingsFormatFactory can be registered by calling SetPostingsFormatFactory(IPostingsFormatFactory) at application startup.