better encoding with $clone

[paulz]

this fragment repeats 3 times:

ViewSnapshots/AppTests/Snapshots/RainbowGlowView.json

Lines 555 to 618 in 1daf838

	{
	"__CACodingContents" : [
	"allowsEdgeAntialiasing",
	"allowsGroupOpacity",
	"anchorPoint",
	"bounds",
	"contentsFormat",
	"contentsGravity",
	"contentsScale",
	"delegate",
	"needsDisplayOnBoundsChange",
	"opaque",
	"position",
	"rasterizationScale",
	"shadowColor",
	"shadowOffset",
	"shadowOpacity",
	"shadowRadius"
	],
	"$class" : "CALayer",
	"allowsEdgeAntialiasing" : false,
	"allowsGroupOpacity" : true,
	"anchorPoint" : {
	"$class" : "LKNSValueCodingProxy",
	"kind" : 0,
	"x" : 0,
	"y" : 0
	},
	"bounds" : {
	"$class" : "LKNSValueCodingProxy",
	"height" : 40.666667938232422,
	"kind" : 2,
	"width" : 195.33332824707031,
	"x" : 0,
	"y" : 0
	},
	"contentsFormat" : "Automatic",
	"contentsGravity" : "bottomLeft",
	"contentsScale" : 3,
	"needsDisplayOnBoundsChange" : false,
	"opaque" : false,
	"position" : {
	"$class" : "LKNSValueCodingProxy",
	"kind" : 0,
	"x" : 52.333332061767578,
	"y" : 79.666664123535156
	},
	"rasterizationScale" : 3,
	"shadowColor" : {
	"$class" : "LKCGColorCodingProxy",
	"a" : 0.33000001311302185,
	"b" : 0,
	"g" : 0,
	"r" : 0
	},
	"shadowOffset" : {
	"$class" : "LKNSValueCodingProxy",
	"height" : 0,
	"kind" : 1,
	"width" : 0
	},
	"shadowOpacity" : 1,
	"shadowRadius" : 2
	},

add $clone similar to $alias to create a clone from known objects

this way object with same properties can be stored more compact