C API 0.99.8

Minor feature release

New features

• Add tsk_treeseq_genetic_relatedness for calculating genetic relatedness between
  pairs of sets of nodes (@brieuclehmann, #1021, #1023, #974, #973, #898).

• Exposed tsk_table_collection_set_indexes to the API
  (@benjeffery, #870, #921).

Breaking changes

• Added an options argument to tsk_table_collection_equals
  and table equality methods to allow for more flexible equality criteria
  (e.g., ignore top-level metadata and schema or provenance tables).
  Existing code should add an extra final parameter 0 to retain the
  current behaviour (@mufernando, @jeromekelleher,
  #896, #897, #913, #917).

• Changed default behaviour of tsk_table_collection_clear to not clear
  provenances and added options argument to optionally clear provenances
  and schemas (@benjeffery, #929, #1001).

• Renamed tsk_treeseq_trait_regression to tsk_treeseq_trait_linear_model.