Introduce a new syntax for specifying an ORDER BY clause

Introduce a new syntax for specifying an ORDER BY clause
(while retaining the old syntax).  For example:

{
    "select":{ "au":[ "family_name", "id" ] },
    "from": "au",
    "order_by":
    [
        {
            "class":"au",
            "field":"family_name",
            "direction":"D"
        },
        {
            "class":"au",
            "field":"id"
        }
    ]
}

This syntax is more flexible than the old syntax, because columns
from the same table don't have to be grouped together.

Planned but not yet implemented: "transform" and "params" tag for
passing a column through a transforming function.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@13035 dcc99617-32d9-48b4-a31d-7c20da2025e4