Build, test, and doc update

Rename `append` and `prepend` to `append_list` and `prepend_list`, add `Bwd.append` #125

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Run time

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Job	Run time
run (4.12)	6m 1s
run (4.14)	6m 7s
run (5.1, true)	6m 21s
	18m 29s