fix release date
add gt_region_mapping_get_sequence_length()
implement additional cases
make sure GtSeqCol is loaded
fix sorting when mixing MD5/non-MD5 seqids
remove generated docs from repo
extend clean targets for documentation
docu formatting
remove unnecessary gt_ prefix
fix memleak
add gt_bioseq_get_encoded_sequence()

and gt_bioseq_get_encoded_sequence_range()
improve performance
implement description retrieval for non-MD5
cosmetics