On relevance being false(), the data node is removed on save, not submission

The spec says when the relevance is false() the data node and its descendants are removed on submission. ODK Collect stores them in memory while the application is open, it persists the relevant values on save and thus on submission. Not sure what Enketo does and that's why I've filed this issue.

Start with issue #153 by comparing the specification's submission wording with the reported ODK Collect behavior and checking the corresponding Enketo behavior. Done means resolving the discrepancy and clarifying the specification's expected timing for removing the data node and descendants.

Written by the indexing model from the issue text.