Add `align` argument to GraphGroup.create_graph and handle NaN's

This MR adds the align argument to GraphGroup.create_graph which is then passed on to GraphGroup.set_<node/edge>_property.

With this MR, missing (NaN) values in the node and edge data are automatically dropped (ignored).

Finally, the MR slightly improves the warning on changed node number in set_node_property.

Anything to double-check?

Don't think so.

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped to 0.16.0a1
  • Reviewed & approved by @herdeanu or @blsqr

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