Implement collection home page

Shows the following fields if they exist:
* title
* logo
* introductory text
* news (also referred to as sidebarText)
* copyright text
* license

Fixes https://github.com/DSpace/dspace-angular/issues/63

src/backend/bitstreams.ts

@@ -63,5 +63,18 @@ export const BITSTREAMS = [
     ],
     "format": "Text",
     "mimetype": "text/plain"
-  }
+  },
+  {
+    "_links": {
+      "self": { "href": "/bitstreams/4688" },
+    },
+    "id": "4688",
+    "uuid": "1bb1be24-c934-41e3-a0fb-ca7a71ab0e71",
+    "type": "bitstream",
+    "name": "collection-5179-logo.png",
+    "size": 299832,
+    "url": "/bitstreams/1bb1be24-c934-41e3-a0fb-ca7a71ab0e71/retrieve",
+    "format": "PNG",
+    "mimetype": "image/png"
+  },
 ];

src/backend/collections.ts

@@ -5,7 +5,8 @@ export const COLLECTIONS = [
       "items": [
         { "href": "/items/8871" },
         { "href": "/items/9978" }
-      ]
+      ],
+      "logo": { "href": "/bitstreams/4688" }
     },
     "id": "5179",
     "uuid": "9e32a2e2-6b91-4236-a361-995ccdc14c60",