Added CMS_HOOK_CACHE, and admin cache.

Prepared evolution of feed module, by allowing json object to list feeds locations.
   The associated key will be used to identify the location, and have category filter by location.

modules/feed_aggregator/feed_aggregator_module.e

@@ -23,6 +23,8 @@ inherit
 
 	CMS_HOOK_MENU_SYSTEM_ALTER
 
+	CMS_HOOK_CACHE
+
 create
 	make
 
@@ -181,10 +183,24 @@ feature -- Hooks configuration
 			a_response.hooks.subscribe_to_block_hook (Current)
 			a_response.hooks.subscribe_to_response_alter_hook (Current)
 			a_response.hooks.subscribe_to_menu_system_alter_hook (Current)
+			a_response.hooks.subscribe_to_cache_hook (Current)
 		end
 
 feature -- Hook
 
+	clear_cache (a_cache_id_list: detachable ITERABLE [READABLE_STRING_GENERAL]; a_response: CMS_RESPONSE)
+			-- <Precursor>.
+		local
+			p: PATH
+			dir: DIRECTORY
+		do
+			p := a_response.api.files_location.extended (".cache").extended (name)
+			create dir.make_with_path (p)
+			if dir.exists then
+				dir.recursive_delete
+			end
+		end
+
 	block_list: ITERABLE [like {CMS_BLOCK}.name]
 			-- List of block names, managed by current object.
 		local