[data-shapes] Pull Request: #222, #288: Update SHACL-SHACL for general NodeExpression and SelectExpression

ajnelson-nist has just submitted a new pull request for https://github.com/w3c/data-shapes:

== #222, #288: Update SHACL-SHACL for general NodeExpression and SelectExpression ==
This PR is built on a not-currently-merged state of #297 .  297 should be merged before this.

This PR is scoped to SHACL-SHACL updates specific to #222 and #288 .  A group decision is not in place on by when this should be merged, or if it blocks PRs or Issues.

This PR is also in a draft status while updates are made over `6bf5a7c`, in response to comments on [this commit](https://github.com/w3c/data-shapes/commit/8632a3e0067c5bfde8f70de79a669b1e3d95e9f5).

See https://github.com/w3c/data-shapes/pull/302


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