Factor crypto stuff out of MatrixClient

Introduce a new Crypto class which encapsulates all of the the crypto-related
gubbins, replacing it with thin wrappers in MatrixClient.

lib/base-apis.js

@@ -705,7 +705,7 @@ MatrixBaseApis.prototype.search = function(opts, callback) {
  * @param {Object} content  body of upload request
  *
  * @param {Object=} opts
-
+ *
  * @param {string=} opts.device_id  explicit device_id to use for upload
  *    (default is to use the same as that used during auth).
  *
@@ -730,6 +730,56 @@ MatrixBaseApis.prototype.uploadKeysRequest = function(content, opts, callback) {
     );
 };
 
+/**
+ * Download device keys
+ *
+ * @param {string[]} userIds  list of users to get keys for
+ *
+ * @param {module:client.callback=} callback
+ *
+ * @return {module:client.Promise} Resolves: result object. Rejects: with
+ *     an error response ({@link module:http-api.MatrixError}).
+ */
+MatrixBaseApis.prototype.downloadKeysForUsers = function(userIds, callback) {
+    var downloadQuery = {};
+
+    for (var i = 0; i < userIds.length; ++i) {
+        downloadQuery[userIds[i]] = {};
+    }
+    var content = {device_keys: downloadQuery};
+    return this._http.authedRequestWithPrefix(
+        callback, "POST", "/keys/query", undefined, content,
+        httpApi.PREFIX_UNSTABLE
+    );
+};
+
+/**
+ * Claim one-time keys
+ *
+ * @param {string[][]} devices  a list of [userId, deviceId] pairs
+ *
+ * @param {module:client.callback=} callback
+ *
+ * @return {module:client.Promise} Resolves: result object. Rejects: with
+ *     an error response ({@link module:http-api.MatrixError}).
+ */
+MatrixBaseApis.prototype.claimOneTimeKeys = function(devices, callback) {
+    var queries = {};
+
+    for (var i = 0; i < devices.length; ++i) {
+        var userId = devices[i][0];
+        var deviceId = devices[i][1];
+        var query = queries[userId] || {};
+        queries[userId] = query;
+        query[deviceId] = "curve25519";
+    }
+    var content = {one_time_keys: queries};
+    return this._http.authedRequestWithPrefix(
+        callback, "POST", "/keys/claim", undefined, content,
+        httpApi.PREFIX_UNSTABLE
+    );
+};
+
 
 // Identity Server Operations
 // ==========================