pgsql: Allow CREATE/ALTER DATABASE to manipulate datistemplate and data

Allow CREATE/ALTER DATABASE to manipulate datistemplate and datallowconn.

Historically these database properties could be manipulated only by
manually updating pg_database, which is error-prone and only possible for
superusers. But there seems no good reason not to allow database owners to
set them for their databases, so invent CREATE/ALTER DATABASE options to do
that. Adjust a couple of places that were doing it the hard way to use the
commands instead.

Vik Fearing, reviewed by Pavel Stehule

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/fbb1d7d73f8e23a3a61e702629c53cef48cb0918

Modified Files
--------------
contrib/pg_upgrade/pg_upgrade.c | 10 ++--
doc/src/sgml/ref/alter_database.sgml | 22 +++++++++
doc/src/sgml/ref/create_database.sgml | 24 +++++++++
src/backend/commands/dbcommands.c | 86 +++++++++++++++++++++++++++++----
src/bin/initdb/initdb.c | 6 +--
src/bin/pg_dump/pg_dumpall.c | 10 ++--
src/bin/psql/tab-complete.c | 7 +--
7 files changed, 135 insertions(+), 30 deletions(-)