Creates a new PublicNexusReader.
Creates a reader for the specified blocks.
The first argument is integer with bits that is composed of bits from PublicNexusReader::NexusBlocksToRead, indicating which of the public blocks should be read. Either compose the argument by ORing together bits (such as NEXUS_TREES_BLOCK_BIT|NEXUS_TAXA_BLOCK_BIT) or simply pass in -1 to read all public blocks. The "standard" NCL NxsBlock (NxsCharactersBlock, NxsTaxaBlock...) instances will be created as initial clone block templates in the contained NxsCloneBlockFactory. These instances can be altered by using getting pointers to them using the GetAssumptionsBlockTemplate(), GetTaxaBlockTemplate()... methods.