Remove unused database parameters from settings.py

As they were useful as example, also add a section on specifying a different
database in the INSTALL documentation.

INSTALL

@@ -1,8 +1,8 @@
 How to start using authentic ?
 ==============================
 
-Eventually modify the settings.py file if you want to use another database
-backend than sqlite3.
+Eventually create a local_settings.py if you want to modify things like
+the database to use.
 
 Then launch the following commands:
 
@@ -19,3 +19,23 @@ You should see the following output:
 	Quit the server with CONTROL-C.
 
 You can access the running application on http://127.0.0.1:8000/
+
+
+Specifying a different database
+-------------------------------
+
+This is done by modifying the DATABASES dictionary in your local_settings.py file;
+for example::
+
+  DATABASES['default'] = {
+    'ENGINE': 'django.db.backends.postgresql',
+    'NAME': 'authentic',
+    'USER': 'admindb',
+    'PASSWORD': 'foobar',
+    'HOST': 'db.example.com',
+    'PORT': '', # empty string means default value
+  }
+
+You should refer to the Django documentation on databases settings at
+http://docs.djangoproject.com/en/dev/ref/settings/#databases for all
+the details.

settings.py

@@ -15,12 +15,8 @@ MANAGERS = ADMINS
 
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.sqlite3', # Add 'postgresql_psycopg2', 'postgresql', 'mysql', 'sqlite3' or 'oracle'.
-        'NAME': os.path.join(PROJECT_PATH, 'authentic.db'),                  # Or path to database file if using sqlite3.
-        'USER': '',                              # Not used with sqlite3.
-        'PASSWORD': '',                          # Not used with sqlite3.
-        'HOST': '',                              # Set to empty string for localhost. Not used with sqlite3.
-        'PORT': '',                              # Set to empty string for default. Not used with sqlite3.
+        'ENGINE': 'django.db.backends.sqlite3',
+        'NAME': os.path.join(PROJECT_PATH, 'authentic.db'),
     }
 }