Add Fiio M3K and Shanling Q1 manuals

Includes installation instructions and a description of Rockbox's
limitations versus the original firmware. Some things are still
missing, notably screenshots for the Q1. The M3K image also needs
to be updated to include the 'select' button.

Change-Id: Ib533206df01925203edeccdd75e1bf22f407e794

manual/rockbox_interface/main.tex

@@ -715,6 +715,23 @@ To turn on and off your Rockbox enabled \dap{} use the following keys:
     and then press the \ButtonPower{} button.
     }
 
+  \opt{fiiom3k,shanlingq1}
+    {
+    Rockbox has a dual-boot feature. To boot into the original firmware,
+    hold \ActionBootOFPlayer{} when powering on the \dap{}.
+
+    You can trigger a normal \playerman{} firmware update by holding
+    \ActionBootOFRecovery{} when powering on the \dap{}.
+    \warn{Updating the original firmware will \textbf{erase} the Rockbox
+      bootloader.}
+
+    \subsection{Entering the recovery menu}
+    You can access the Rockbox bootloader's ``recovery menu'' by holding
+    \ActionBootRecoveryMenu{}. This menu can be used to connect your \dap{}
+    over USB to transfer files, update the Rockbox bootloader, or revert to a
+    bootloader you've previously backed up.
+    }
+
   }
 \subsection{Putting music on your \dap{}}