added cast function for timestamp type
fix alter table add column on partitioned tables
make setNextRow in FilterProjector synchronized

Fixes a race conditation where rows weren't filtered but
should have been. (Or the other way around).

The collectorExpression/condition that is used there
contains shared state and setNextRow is called from different
threads.

testHavingGroupByNonDistributed failed about 3 times in 800
runs.
fix: support alter number_of_shards