Make /cache/recovery/last_log available in recovery

Create a new recovery UI option to allow the user to view
/cache/recovery/last_log for their device. This gives enhanced
debugging information which may be necessary when a failed
OTA occurs.

Bug: 18094012
Change-Id: Ic3228de96e9bfc2a0141c7aab4ce392a38140cf3

default_device.cpp

@@ -31,6 +31,7 @@ static const char* ITEMS[] =  {"reboot system now",
                                "wipe cache partition",
                                "reboot to bootloader",
                                "power down",
+                               "view recovery logs",
                                NULL };
 
 class DefaultDevice : public Device {
@@ -69,6 +70,7 @@ class DefaultDevice : public Device {
           case 3: return WIPE_CACHE;
           case 4: return REBOOT_BOOTLOADER;
           case 5: return SHUTDOWN;
+          case 6: return READ_RECOVERY_LASTLOG;
           default: return NO_ACTION;
         }
     }