GH-242: Support multiple queue bindings

Resolves https://github.com/spring-cloud/spring-cloud-stream-binder-rabbit/issues/242

Allow a consumer binding to bind its queue with multiple routing keys.

Add `bindingQueueDelimiter` to treat `bindingRoutingKey` as a list.
Resolves #266

docs/src/main/asciidoc/overview.adoc

@@ -139,9 +139,14 @@ Whether to automatically declare the DLQ and bind it to the binder DLX.
 Default: `false`.
 bindingRoutingKey::
 The routing key with which to bind the queue to the exchange (if `bindQueue` is `true`).
-For partitioned destinations, `-<instanceIndex>` is appended.
+Can be multiple keys - see `bindingRoutingKeyDelimiter`.
+For partitioned destinations, `-<instanceIndex>` is appended to each key.
 +
 Default: `#`.
+bindingRoutingKeyDelimiter::
+When this is not null, 'bindingRoutingKey' is considered to be a list of keys delimited by this value; often a comma is used.
++
+Default: `null`.
 bindQueue::
 Whether to declare the queue and bind it to the destination exchange.
 Set it to `false` if you have set up your own infrastructure and have previously created and bound the queue.
@@ -420,10 +425,16 @@ The batch timeout when batching is enabled.
 Default: `5000`.
 bindingRoutingKey::
 The routing key with which to bind the queue to the exchange (if `bindQueue` is `true`).
-Only applies to non-partitioned destinations.
+Can be multiple keys - see `bindingRoutingKeyDelimiter`.
+For partitioned destinations, `-n` is appended to each key.
 Only applies if `requiredGroups` are provided and then only to those groups.
 +
 Default: `#`.
+bindingRoutingKeyDelimiter::
+When this is not null, 'bindingRoutingKey' is considered to be a list of keys delimited by this value; often a comma is used.
+Only applies if `requiredGroups` are provided and then only to those groups.
++
+Default: `null`.
 bindQueue::
 Whether to declare the queue and bind it to the destination exchange.
 Set it to `false` if you have set up your own infrastructure and have previously created and bound the queue.