Fix the combination of updating a table which contains an LOB, and reading from the LOB at the same time.
Previously it would throw an exception, now it works.

Use a weak dependency to the JTS jar file (allow to use H2 without the JTS jar file in the classpath)

Use a weak dependency to the JTS jar file (allow to use H2 without the JTS jar file in the classpath)

Save some memory. There is no need to store a dataType field in the AggregateData structure when we can just pass it down. 

make some field names in Aggregate more obvious, to distinguish the special case GROUP_CONCAT fields from the normal fields

The purpose of this is to simplify the code for the individual cases to make it easier to implement analytic (windowing) functions.

for the "duplicate key exception" test, make it a little more flexible, because the format of the VALUES clause varies a little depending on the type of the index.