core: Use methods to access bridge information

Bridge information were exposed and accessed via public constants
which doesn't work if you want to generate bridges dynamically as
discussed in #402

lib/BridgeInterface.php

@@ -13,6 +13,13 @@ interface BridgeInterface {
 	 */
 	public function getCachable();
 
+	/**
+	 * Returns the description
+	 *
+	 * @return string Description
+	 */
+	public function getDescription();
+
 	/**
 	 * Return an array of extra information
 	 *
@@ -27,6 +34,13 @@ interface BridgeInterface {
 	 */
 	public function getItems();
 
+	/**
+	 * Returns the bridge maintainer
+	 *
+	 * @return string Bridge maintainer
+	 */
+	public function getMaintainer();
+
 	/**
 	 * Returns the bridge name
 	 *
@@ -34,6 +48,13 @@ interface BridgeInterface {
 	 */
 	public function getName();
 
+	/**
+	 * Returns the bridge parameters
+	 *
+	 * @return array Bridge parameters
+	 */
+	public function getParameters();
+
 	/**
 	 * Returns the bridge URI
 	 *