Improved Adminmenu

All first level menu items of the new admin menu are clickable directly now.

The menu item of the 1st Level called "Plugins" opens the Pluginmanager, the menu item "Files" opens the filemanager, calling the folder "user files".

There was another problem: The Plugins menu was too long, if many plugins was installed. Now there is a "3 columns Plugins menu", if there are a defined number of plugins are installed.

From how many plugins the "3 columns Plugins menu" is active, is configurable.

Moreover, you can remove rarely used plugins from the Plugins menu (via Pluginmanager), so the plugins menu is more clear.