config: set default database connection settings.

Set sensible defaults for connecting to the database. By default, we try
to connect to the `danbooru2` database running on localhost as the
`danbooru` user. These are the defaults recommended by the install
guide.

If you need to change the database settings, set DATABASE_URL in
.env.local or on the command line:

   # .env.local
   DATABASE_URL=postgresql://danbooru:password@localhost/danbooru2

   # command line
   $ DATABASE_URL=postgresql://danbooru:password@localhost/danbooru2 bin/rails server

This eliminates the need to copy script/install/database.yml.templ to
config/database.yml during installation and during deployment. This is
so that Danbooru works out of the box without extra configuration. In
particular, this is so that we can run Danbooru in a Docker container
without having to set DATABASE_URL.

script/install/database.yml.templ

@@ -1,45 +0,0 @@
-# SQLite version 3.x
-#   gem install sqlite3-ruby (not necessary on OS X Leopard)
-development:
-  adapter: postgresql
-  database: danbooru2
-  pool: 5
-  timeout: 5000
-  url: <%= ENV['DATABASE_URL'] %>
-
-# Warning: The database defined as "test" will be erased and
-# re-generated from your development database when you run "rake".
-# Do not set this db to the same as development or production.
-test:
-  adapter: postgresql
-  database: danbooru2_test
-  pool: 5
-  timeout: 5000
-  url: <%= ENV['DATABASE_URL'] %>
-
-production:
-  adapter: postgresql
-  database: danbooru2
-  pool: 5
-  timeout: 5000
-  url: <%= ENV['DATABASE_URL'] %>
-
-archive_development:
-  adapter: postgresql
-  database: archive_development
-  url: <%= ENV['ARCHIVE_DATABASE_URL'] %>
-
-archive_test:
-  adapter: postgresql
-  database: archive_test
-  url: <%= ENV['ARCHIVE_DATABASE_URL'] %>
-
-archive_production:
-  adapter: postgresql
-  database: archive_development
-  url: <%= ENV['ARCHIVE_DATABASE_URL'] %>
-
-archive_staging:
-  adapter: postgresql
-  database: archive_development
-  url: <%= ENV['ARCHIVE_DATABASE_URL'] %>