[entity/optimization] Cache rset when entity.related is called with entities=False
If fail to see why we couldn't cache in this case, while this is important for
optimization reason: when doing a single HTTP request, some queries are done two
or three times because of predicates / uicfg or alike.
Also always store tuple and not list in the cache, because:
* else we get some regression
* and inconsistent result type (tuple or list)
* and it simply feels better to cache an unmutable object.
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/*