[Fix] Ensure nested repeats are shown when relevance is true

[eyelidlessness]

Fixes enketo/enketo#103. This is branched off of master, unlike enketo/enketo-core#806 which we should likely close.

Some of these tests are likely redundant, but it was hard for me to be sure, so I felt more comfortable adding them.

[MartijnR]

Thanks for tackling a nested repeat issue! I am committing to doing a review.