Add interface that will be used by plugins

Wox.Plugin/Interfaces/IReloadable.cs

@@ -0,0 +1,18 @@
+namespace Wox.Plugin
+{
+    /// <summary>
+    /// This interface is to indicate and allow plugins to reload their
+    /// in memory data cache or other mediums when user makes a new change
+    /// that is not immediately captured. For example, for BrowserBookmark and Program
+    /// plugin does not automatically detect when a user added a new bookmark or program,
+    /// so this interface's function is exposed to allow user manually do the reloading after 
+    /// those new additions.
+    /// 
+    /// The command that allows user to manual reload is exposed via Plugin.Sys, and
+    /// it will call the plugins that have implemented this interface.
+    /// </summary>
+    public interface IReloadable
+    {
+        void ReloadData();
+    }
+}