Refactor sequence and annotation reverse complementation

[standage]

This update renames the rev_complement_anno function to reverse_complement, and replaces the rev_comp_uas_output_bracket function with a new reverse_complement_bracketed function that is clearer and more concise. Both are drop-ins for the original functions: no other changes are required except to call the new function names.

Both functions were moved to the new repeat module. This is the logical home for the latter function, and for import reasons it was convenient to keep them together.

[standage]

Ready for review and merge.