Adding MultiBackend driver (VUFIND-643).

config/vufind/MultiBackend.ini

+[General]
+; This setting controls the MultiBackend driver's behavior when it can't
+; determine which specific driver should be used to service a particular
+; request. Select "use_first" if you would like MultiBackend to return
+; the value generated by the first driver capable of responding to the
+; specified method; select "merge" if you would like all potentially
+; relevant responses to be combined into a single response (only works
+; for array-oriented data).
+default_fallback_driver_selection = use_first
+
+; (Optional) The name of a driver instance to use by default if no specific
+; instance can be determined as the best option (must correspond with a key
+; from the [Drivers] section below if set -- omit to have no default driver)
+;default_driver = "instance1"
+
+; This section is for declaring which driver to use for each institution.
+; The key should be the Source ID of a specific institution, and the value
+; should be the name of an ILS driver.
+;      Example: instance1 = Voyager
+; In this case, the Voyager driver would be loaded and configured using an
+; instance1.ini file (which you should create as a copy of Voyager.ini).
+[Drivers]
+;instance1 = Voyager
+;instance2 = Voyager
+;instance3 = Unicorn
+;instance4 = Voyager
+
+; This section allows for the use of custom delimeters between user data
+; and the identifying information that allows the MultiBackend driver to
+; determine which internal driver to use for a given request.
+;
+; Currently only custom login delimiters are supported.
+;
+; You should not set the delimiters to be common characters.
+[Delimiters]
+login = "	"
+
+; This section allows you to override the default functionality set by
+; default_fallback_driver_selection on a method-by-method basis. See above
+; for explanations of legal values (merge/use_first)
+[FallbackDriverSelectionOverride]
+;getMyFines = merge