Update property nesting

Deeper nested properties guaranteed to be processed after shallower
nested properties.

Also added strict mode checks for duplicate nested properties.

docs/tut/crash-course/7-property-groups.md

@@ -1,101 +0,0 @@
-# Property Groups
-
-Often when creating components from existing components, you can find yourself
-repetitively passing through properties such as size or position.
-
-Example below:
-
-```lua
-function Background(props: {
-    Color: Color3,
-    AnchorPoint: UDim2,
-    Position: UDim2,
-    Size: UDim2
-})
-    return create "Frame" {
-        Color = props.Color
-        AnchorPoint = props.AnchorPoint,
-        Position = props.Position,
-        Size = props.Size
-    }
-end
-
-function Menu(props: {
-    Color = props.Color
-    AnchorPoint: UDim2,
-    Position: UDim2,
-    Size: UDim2
-})
-    return Background {
-        Color = props.COlor,
-        AnchorPoint = props.AnchorPoint,
-        Position = props.Position,
-        Size = props.Size
-    }
-end
-```
-
-One way this can be avoided is by using *property nesting*. In Vide, passing a
-table value inside `props` has special semantics. Any key with a table value is
-not assigned like a property, instead the table is iterated and processed just
-like the outer table is. Any properties in the nested table will be assigned
-to the instance just the same.
-
-Below is an example of how you can use this to pass groups of similar properties
-together such as position and size, while also using typechecking.
-
-```lua
-type Layout = {
-    Layout = {
-        Position: UDim2?,
-        Size: UDim2?,
-        AnchorPoint: Vector2?
-    }
-}
-
-function Background(props: Layout & { Color: Color3 })
-    return create "Frame" {
-        Color = props.Color,
-        props.Layout
-    }
-end
-
-function Menu(props: Layout & { Color: Color3 })
-    return Background {
-        Color = props.Color,
-        Layout = props.Layout
-    }
-end
-```
-
-Here we created a nested group with the key `Layout` that can accept
-layout-related properties. Any name could be chosen for the key.
-This allows us to write much more concise syntax that is also typecheckable.
-
-In another example we use a key named `Children` to pass arrays of instances to
-be parented.
-
-```lua
-type Children = {
-    Children = Array<Instance>
-}
-
-local function List(props: Children & Layout)
-    return create "Frame" {
-        props.Layout,
-        props.Children,
-        create "UIListLayout" {}
-    }
-end
-
-List {
-    Layout = {
-        Position = UDim2.new()
-    },
-
-    Children = {
-        create "TextLabel" { Text = "1" },
-        create "TextLabel" { Text = "2" }
-    }
-}
-```