add remove method for offline account cache used by MFA

vendor/priors/gwt.js

@@ -1161,6 +1161,7 @@ var accountCache = {
         });
     };
 	this.setLoginData = setLoginDataIntoCacheProm;
+	this.remove = removeLoginDataFromCacheProm;
 	this.getEntryData = getEntryDataFromCacheProm;
     }
 };
@@ -1184,6 +1185,21 @@ function setLoginDataIntoCacheProm(key, entryPoints) {
     return future;
 }
 
+function removeLoginDataFromCacheProm(key) {
+    let future = peergos.shared.util.Futures.incomplete();
+    if (!this.isCachingEnabled) {
+        future.complete(true);
+    } else {
+        let that = this;
+        setIDBKV(key, [], this.cacheAccountStore).then(() => {
+            future.complete(true);
+        }).catch(err => {
+            future.complete(true);
+        });
+    }
+    return future;
+}
+
 //      public native CompletableFuture<byte[]> getEntryData(String key);
 function getEntryDataFromCacheProm(key) {
     let that = this;