Add `clearCache`, `cleanExpiredCache` function

Sources/Cache/ImageCache.swift

@@ -588,6 +588,15 @@ open class ImageCache {
     }
 
     // MARK: Cleaning
+    /// Clears the memory & disk storage of this cache. This is an async operation.
+    ///
+    /// - Parameter handler: A closure which is invoked when the cache clearing operation finishes.
+    ///                      This `handler` will be called from the main queue.
+    public func clearCache(completion handler: (() -> Void)? = nil) {
+        clearMemoryCache()
+        clearDiskCache(completion: handler)
+    }
+    
     /// Clears the memory storage of this cache.
     @objc public func clearMemoryCache() {
         try? memoryStorage.removeAll()
@@ -597,7 +606,7 @@ open class ImageCache {
     ///
     /// - Parameter handler: A closure which is invoked when the cache clearing operation finishes.
     ///                      This `handler` will be called from the main queue.
-    open func clearDiskCache(completion handler: (()->())? = nil) {
+    open func clearDiskCache(completion handler: (() -> Void)? = nil) {
         ioQueue.async {
             do {
                 try self.diskStorage.removeAll()
@@ -607,6 +616,12 @@ open class ImageCache {
             }
         }
     }
+    
+    /// Clears the expired images from memory & disk storage. This is an async operation.
+    open func cleanExpiredCache(completion handler: (() -> Void)? = nil) {
+        cleanExpiredMemoryCache()
+        cleanExpiredDiskCache(completion: handler)
+    }
 
     /// Clears the expired images from disk storage. This is an async operation.
     open func cleanExpiredMemoryCache() {