main menu: Add the ability to hide and reorder the main menu items.

To change the shown menu items add the line "root_menu_order:<items>" into your config.cfg
<items> can be any of:
bookmarks, files, database, wps, settings, recording, radio, playlists, plugins, system_menu, shortcuts

Manual entry by Alexander Levin

Change-Id: Ie7f4bfb0f795184de094d05fc341a6cedd1c0cde
Reviewed-on: http://gerrit.rockbox.org/104
Reviewed-by: Jonathan Gordon <rockbox@jdgordon.info>

manual/advanced_topics/main.tex

@@ -2,6 +2,29 @@
 \chapter{Advanced Topics}
 
 \section{\label{ref:CustomisingUI}Customising the User Interface}
+
+\subsection{\label{ref:CustomisingTheMainMenu}Customising The Main Menu}
+
+It is possible to customise the main menu, i.e. to reorder or to hide some
+of its items. To accomplish this, the file \fname{/.rockbox/config.cfg} must
+be edited (presumably on the computer while the \dap{} is connected to it
+via USB). There, the line starting with \config{root\_menu\_order:} must
+be edited (or created if it is not present yet).
+
+The line should look like \config{root\_menu\_order:items}, where ``items''
+is a comma separated list (no spaces around the commas!) of the following
+words: \config{bookmarks}, \config{files}, \opt{database}{\config{database}, }%
+\config{wps}, \config{settings}, \opt{recording}{\config{recording}, }%
+\opt{radio}{\config{radio}, }\config{playlists}, \config{plugins},
+\config{system\_menu}, \opt{PLAYER_PAD}{\config{shutdown}, }\config{shortcuts}.
+Each of the words, if it occurs in the list, activates the appropriate item
+in the main menu. The order of the items is given by the order of the words
+in the list. The items whose words do not occur in the list will be hidden,
+with one exception: the menu item ``Settings'' will be shown even if its word
+is not in the list (it is added as the last item then).
+
+Only the main menu can be customised this way, submenus can not.
+
 \opt{lcd_bitmap}{
 \subsection{\label{ref:GettingExtras}Getting Extras}