Move createNewMatrixCall to the client object

So we can mock it out it tests (and also I'm not sure why it was
like this in the first place: we passed the client in anyway...)

Deprecate createNewMatrixCall

src/client.js

@@ -729,6 +729,17 @@ MatrixClient.prototype.setSupportsCallTransfer = function(supportsCallTransfer)
     this._supportsCallTransfer = supportsCallTransfer;
 };
 
+/**
+ * Creates a new call.
+ * The place*Call methods on the returned call can be used to actually place a call
+ *
+ * @param {string} roomId The room the call is to be placed in.
+ * @return {MatrixCall} the call or null if the browser doesn't support calling.
+ */
+MatrixClient.prototype.createCall = function(roomId) {
+    return createNewMatrixCall(this, roomId);
+};
+
 /**
  * Get the current sync state.
  * @return {?string} the sync state, which may be null.