Saxon SQL extension instructions

A new sql:query instruction has been added, to accompany the existing sql:connect, sql:insert, etc.

Attributes:

table	The table to be queried (the contents of the FROM clause of the select statement). This is mandatory, the value is an attribute value template.
column	The columns to be retrieved (the contents of the SELECT clause of the select statement). May be "*" to retrieve all columns. This is mandatory, the value is an attribute value template.
where	The conditions to be applied (the contents of the WHERE clause of the select statement). This is optional, if present the value is an attribute value template.
row-tag	The element name to be used to contain each row. Must be a simple name (no colon allowed). Default is "row".
column-tag	The element name to be used to contain each column. Must be a simple name (no colon allowed). Default is "col".

The sql:query instruction writes zero or more row elements to the current result tree, each containing zero or more column elements, which contain the data values.

Thanks to Claudio Thomas [claudio.thomas@web.de] who supplied the original version of this code.

The SQL extensions are now contained in a separate JAR file, saxon7-sql.jar, which must be on the class path if these extensions are used.