set session_replication_role to local in the apply trigger when performing DDL

This fixes bug 305 where user defined (non-replication) triggers don't fire during
the remote/replica exection of EXECUTE_SCRIPT commands
Fixes to DDL test (old regression)
Merge branch 'bug305'
updating release notes
bug 304 - record sequence values as part of a EXECUTE_SCRIPT

Prior to 2.2 the EXECUTE_SCRIPT command result in a DDL_SCRIPT event
and a SYNC event generated as part of the same transaction. That
SYNC event also replicates the value of any sequences to the replica
before the DDL SCRIPT command.

In 2.2 the DDL script is replicated as part of a normal SYNC
as rows in sl_log_script.  This commit stores any sequence changes
as extra elements in the cmdargs array.  These sequence values are
then set before the DDL_SCRIPT is executed on the replica

This commit includes a unit test change to reproduce this issue
the test now passes
Allow the apply trigger to work (ie not fail) on sl_log_script rows from earlier betas of 2.2.0
Revisions to DDL docs
Add release note on #304
Merge branch 'bug304' of github.com:ssinger/slony1-engine into bug304
Fix typo in sample data
Some erroneous queries in date test
create string_agg in slony1_base.sql not slony1_funcs.sql

If the CREATE AGGREGATE is in slony1_funcs.sql it will fail on an update functions
since the aggregate already exists.  As part of the upgrade we will check
to see if we need to create the aggregate.
deconstruct_array wants the OID of the element type, not the array type
Merge branch 'bug304'
bug 309 - make sure sl_failover_targets gets created when upgrading to 2.2