[testlib] put postgres test database in test/data/database directory
with other (sqlite) test databases. Closes #9240765
Simplify .hgignore in passing.
Add some entities
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As manager, you can access to entity creation forms by using the `site management`_ page.
.. _`site management`: ../manage
As regular user, the index page or the action box may propose some links to create entities according to the context.