Add initial feed

The MCU board now lets the printer pull in the carrier until the new
paper in sensor is triggered for the first time and then starts the
print like before. The new "initial feed" provides an alignment of the
carrier which is exactly the same every time. Of course, the carrier now
needs two markings.

src/main.h

@@ -7,14 +7,27 @@
 
 typedef enum
 {
-    PowerOnWait,
-    Idle,
-    ClutchDelay,
-    WaitingForPaperIn,
-    ExitOnDelay,
-    ManualPaperFeedOffDelay,
-    PaperInOffDelay,
-    ExitOffDelay
+    PowerOnWait,                        // Power-on test state with all outputs
+                                        // enabled
+
+    Idle,                               // Waiting for print job
+
+    AlignFeed,                          // Initial pulling in for proper align-
+                                        // ment of the carrier
+
+    ClutchDelay,                        // Delay before main carrier feed
+
+    WaitingForFeed,                     // Waits for the end of the carrier
+                                        // alignment mark
+
+    WaitingForPaperIn,                  // Waits for the paper in mark on the
+                                        // carrier
+
+    ExitOnDelay,                        // Wait for print to be completed
+
+    ManualPaperFeedOffDelay,            // Various delays
+    PaperInOffDelay,                    // for disabling the
+    ExitOffDelay                        // sensor signals again
 } State_t;
 
 int main(void);