Fix destruction of modext panels

Renamed reserver `remove` method to `removeXXX`
Added MODx.unloadRTE('ta') call
Update Ext.ux.grid.RowExpander (old one does not handle destroing correctly)

These changes (and some of others) will help me to release my plugin, wich makes Modx manager panel to use Ajax for page navigation. This will speed up manager page navigation up to 10 times (See http://forums.modx.com/thread/80560/howto-high-speed-manager-panel-page-navigation#dis-post-444144) !