[rset] add convenient first() and last() methods on ResultSet
These make life easier for the heavy user of the CW shell.
Also aliases entities() with all(); so we end with a pretty consistant set:
- .one()
- .first()
- .last()
- .all()
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Changelog history
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.. include:: 3.26.rst
.. include:: 3.25.rst
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.. include:: 3.14.rst