Add support for property groups

test/demo/example.gdextension

@@ -4,5 +4,5 @@ entry_symbol = "example_library_init"
 
 [libraries]
 
-Linux.64 = "bin/x11/libgdexample.so"
-Windows.64 = "bin/win64/libgdexample.dll"
+linux.64 = "bin/x11/libgdexample.so"
+windows.64 = "bin/win64/libgdexample.dll"

test/demo/main.gd

@@ -13,9 +13,9 @@ func _ready():
 	prints("vararg args", $Example.varargs_func("some", "arguments", "to", "test"))
 
 	# Use properties.
-	prints("custom postion is", $Example.custom_position)
-	$Example.custom_position = Vector2(50, 50)
-	prints("custom postion now is", $Example.custom_position)
+	prints("custom position is", $Example.group_subgroup_custom_position)
+	$Example.group_subgroup_custom_position = Vector2(50, 50)
+	prints("custom position now is", $Example.group_subgroup_custom_position)
 
 	# Get constants
 	prints("FIRST", $Example.FIRST)

test/demo/main.tscn

@@ -7,9 +7,6 @@ script = ExtResource( "1_c326s" )
 
 [node name="Example" type="Example" parent="."]
 script = null
-__meta__ = {
-"_edit_use_anchors_": false
-}
 
 [node name="Label" type="Label" parent="Example"]
 offset_left = 194.0