feat(ConfigInterface): add previousPrefix field

Author: DanielKucal

src/config/config.interface.ts

@@ -1,5 +1,6 @@
 export interface WebStorageConfigInterface {
     prefix?: string;
+    previousPrefix?: string;
     clearType?: ClearType;
     mutateObjects?: boolean;
 }

src/utility/webstorage-utility.ts

@@ -15,7 +15,7 @@ export class WebStorageUtility {
         }
     }
 
-    public constructor(storage: Storage, prefix: string) {
+    public constructor(storage: Storage, prefix: string, previousPrefix?: string) {
         this._storage = storage;
         this._prefix = prefix;
     }
@@ -37,6 +37,7 @@ export class WebStorageUtility {
         return value;
     }
 
+    // TODO return true if item existed and false otherwise (?)
     public remove(key: string): void {
         let storageKey = this.getStorageKey(key);
         this._storage.removeItem(storageKey);