Hologram
--------
* This block is only available if digilines is loaded.

Projects a hologram above the hologram node. Also acts as a digilines
conductor.

The hologram occupies a space 15x15x15. The lower level of the hologram
is 2 blocks above the hologram node (so the hologram node can be hidden
beneath a floor). The hologram node is in the x, z horizontal center, ie.
the hologram can extend 7 blocks in each direction from the node.

Colored blocks cannot be interacted with, but will be replaced if built
into. If a block already exists where the hologram requires a color, it
is not placed unless the block is a color block from this hologram block.
If an existing block is dug while a holograms is displayed it is not
filled in, the hologram has to be re-displayed.

Only the owner can dig or access the form of the locked version.

UI

Channel - digilines channel of hologram.

Digilines messages

"clear"
	Removes any hologram currently projected.

table
	To display a hologram a table of dimensions holo[15][15][15] is sent as
	the message. The table structure is holo[layer][line][block]. In the
	direction the hologram block is facing, the layers run from bottom to
	top, the lines run from back to front, and the blocks run from right to
	left. Each block value can be nil for no display, or a string with the
	color. Valid colors are:
		"black"
		"gray"
		"silver"
		"white"
		"sky"
		"blue"
		"cyan"
		"lime"
		"green"
		"magenta"
		"purple"
		"pink"
		"red"
		"yellow"
		"orange"
		"brown"
	If anything else no color block is placed.

	For example:
	{
		{
			{ "black", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "green" },
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{ "blue", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "red" }
		},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{},
		{
			{ "orange", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "lime" },
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{},
			{ "purple", nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, "yellow" }
		},
	}

	will display a hologram with a black and green block at the back of
	the bottom layer, and orange and lime at the back of the top layer.
