Added support for viewpointvalue command (#3754)

Additionally added a script command to update the player's camera.
Added a new atcommand camerainfo for this, which is limited to admins.

Credits to @4144 for finding /setcamera

doc/packet_struct_notation.txt

@@ -59,6 +59,7 @@ values.
  B = 1 byte (byte)
  W = 2 bytes (word)
  L = 4 bytes (long, dword)
+ F = 4 bytes (float)
  Q = 8 bytes (quad)
 
  nB = n bytes