[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()
Document: cubicweb-doc
Title: CubicWeb Documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/python-cubicweb-documentation/html/index.html
Files: /usr/share/doc/python-cubicweb-documentation/html/*