"ZCTextIndex": suboptimal "operators" definition

[d-maurer]

ZCTextIndex defines:

    operators = ('and', 'or')
    useOperator = 'or'

Actually, it ignores operator completely and implements something which is an "and" in simple cases and can be anything in complex (but non sensible) cases.

I suggest to define:

    operators = ()
    useOperator = None  #concatenates the individual search terms separated by space