Add MatrixClient.clearStores

- to clear both sets of storage on logout

src/client.js

@@ -156,8 +156,9 @@ function MatrixClient(opts) {
     this._notifTimelineSet = null;
 
     this._crypto = null;
+    this._cryptoStore = opts.cryptoStore;
     if (CRYPTO_ENABLED && Boolean(opts.sessionStore) &&
-            Boolean(opts.cryptoStore) &&
+            Boolean(this._cryptoStore) &&
             userId !== null && this.deviceId !== null) {
         this._crypto = new Crypto(
             this, this,
@@ -173,6 +174,25 @@ function MatrixClient(opts) {
 utils.inherits(MatrixClient, EventEmitter);
 utils.extend(MatrixClient.prototype, MatrixBaseApis.prototype);
 
+/**
+ * Clear any data out of the persistent stores used by the client.
+ *
+ * @returns {Promise} Promise which resolves when the stores have been cleared.
+ */
+MatrixClient.prototype.clearStores = function() {
+    if (this._clientRunning) {
+        throw new Error("Cannot clear stores while client is running");
+    }
+
+    const promises = [];
+
+    promises.push(this.store.deleteAllData());
+    if (this._cryptoStore) {
+        promises.push(this._cryptoStore.deleteAllData());
+    }
+    return q.all(promises);
+};
+
 /**
  * Get the user-id of the logged-in user
  *