Minor UI improvments & bugfixes

- improved "Copy text" option in right click menu, to display what exactly to copy
- added "Dump selected assets" option to right click menu
- added 'selected assets count' info to status strip when you select assets
- added 'exported count / total export count` info to status strip during export
- "Show error message" option on the "Debug" tab renamed to "Show all error messages" and is now disabled by default
- "fixed" an issue with getting stuck during the "Building tree structure" step
- fixed a bug with listSearch that could make it not work in some conditions
- fixed a rare bug for resource files with the same name, that caused their data to be overwritten and become incorrect

AssetStudio/AssetsManager.cs

@@ -173,9 +173,9 @@ namespace AssetStudio
                     {
                         LoadAssetsFromMemory(subReader, originalPath ?? reader.FullPath, bundleFile.m_Header.unityRevision);
                     }
-                    else
+                    else if (!resourceFileReaders.ContainsKey(file.fileName))
                     {
-                        resourceFileReaders[file.fileName] = subReader; //TODO
+                        resourceFileReaders.Add(file.fileName, subReader);
                     }
                 }
             }