Couchbase UI needs not just list of design documents (which can be
fetched as of now via _all_docs with correctly picket {start,end}key)
but also some additional information about those design documents.

As of now we need to advertise link to compactView controller.

Here's changes:

* bucket details (e.g. /pools/default/buckets/default and elements of
  /pools/default/buckets) gets extra attribute: ddocs as can be seen
  in example:

        ],
        "stats": {
            "uri": "/pools/default/buckets/default/stats",
            "directoryURI": "/pools/default/buckets/default/statsDirectory",
            "nodeStatsListURI": "/pools/default/buckets/default/nodes"
        },
        "ddocs": {
            "uri": "/pools/default/buckets/default/ddocs"
        },
        "nodeLocator": "vbucket",

* ddocs.uri field points to list of ddocs
  (/pools/default/buckets/<bucket-name>/ddocs) that looks like this
  (at the time of writing):

# wget -q -O- --user=Administrator --password=asdasd http://lh:9000/pools/default/buckets/default/ddocs | json_reformat
[
    {
        "id": "_design/t",
        "doc": {
            "_id": "_design/t",
            "_rev": "1-3b6fdd00",
            "views": {
                "t": {
                    "map": "function (doc) {\n  emit(doc._id, null);\n}"
                }
            }
        },
        "controllers": {
            "compact": "/pools/default/buckets/default/ddocs/_design%2Ft/controller/compactView"
        }
    },
    {
        "id": "_design/dev_t",
        "doc": {
            "_id": "_design/dev_t",
            "_rev": "1-c1039472",
            "views": {
                "t": {
                    "map": "function (doc) {\n  emit(doc._id, null);\n}"
                }
            }
        },
        "controllers": {
            "compact": "/pools/default/buckets/default/ddocs/_design%2Fdev_t/controller/compactView"
        }
    }
]
