Added Bitfield.zeros and Bitfield.ones classmethods for constructing an empty bitfield of known size. Bitfield.copy method to copy a bitfield object. SequenceBlock and OptimizedProfileBlock classes to store Python objects next to a contiguous array of pointers for iterating with the GIL released. SequenceFile.read_block method to read a whole sequence block from a file. HMM.sample class method to generate a HMM at random given a Randomness source. hmmscan function to scan a profile database with sequence queries. deepcopy implementations to HMM, Profile and OptimizedProfile classes of plan7. rewind method to HMMFile, HMMPressedFile and SequenceFile to reset a file back to its initial position. name attribute to HMMFile, HMMPressedFile, MSA...