Start of an Iaudio M3 manual: add the necessary platform files (name the remote keyma...

Start of an Iaudio M3 manual: add the necessary platform files (name the remote keymap file 'iaudio' because the keymap is shared with M5 and X5 and could be reused there), add pictures of the remote with labels and place it below the player image, already fill out some installation instructions which are very similar to the other Iaudios. The manual still needs a way to mention main unit and remote control buttons in text descriptions, the second column in the button tables needs to be filled out (using IAUDIO_RC_PAD and adding this to the M5 and X5 platform files) - and screenshots are needed too...

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21645 a1c6a512-1295-4272-9138-f99709370657