Added logic to use the value of 'textindex_operator' as passed in the request to determine which query operator to use (and, near, andnot, or).  Valid values to pass in to textindex_operator are 'and', 'or', 'near', and 'andnot' (capitalization is ignored).  This is a near-term workaround for the inability to specify a default text index query operator on a per-index basis.  It provides the ability to override the currently module-defined default 'Or' operator for textindexes on a per-search basis.

An example of the utility of textindex_operator used with a ZCatalog instance:

zcatalog.searchResults(PrincipiaSearchSource='foo', textindex_operator='and')