In SELECT(): Enhanced the validation of JSON queries:

In SELECT(): Enhanced the validation of JSON queries:

1. If the FROM clause is the wrong sort of jsonObject, issue
a helpful message before bailing out.

2. If a class in the SELECT clause is not defined in the IDL,
issue a message and bail out (instead of silently ignoring it).

3. If a selected item is represented by anything but a
JSON_STRING or JSON_HASH, issue a message and bail out
(instead of creating a query that bombs out later due to an
extra comma).

git-svn-id: svn://svn.open-ils.org/ILS/trunk@12297 dcc99617-32d9-48b4-a31d-7c20da2025e4