This requires them to be both accepted as columns (see change in
isValidColumn) and usable in an abstract syntax tree (see changes in
buildQueryFromAbstractSyntaxTreeNode), requiring a ScriptableKey-to-
SearchKey wrapper (see SearchKeyWrapperForScriptableKey).

Add a test.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36990 20353a03-c40f-0410-a6d1-a30d3c3de9de