Made Advanced installation offer optional packages

Previously all detected content would be installed. Now the user can choose whether they want to install the optional packages like music and videos.

mods/modcontent/chrome.yaml

@@ -109,3 +109,26 @@ scrollpanel-decorations:
 		down-pressed: 453, 512, 16, 16
 		up: 470, 512, 16, 16
 		up-pressed: 470, 512, 16, 16
+
+
+# Checkbox-related definitions:
+
+checkbox:
+	Inherits: ^Chrome
+	PanelRegion: 512, 512, 10, 10, 44, 44, 10, 10
+
+checkbox-hover:
+	Inherits: checkbox
+
+checkbox-pressed:
+	Inherits: checkbox
+
+checkbox-disabled:
+	Inherits: checkbox
+
+checkmark-tick:
+	Inherits: ^Chrome
+	Regions:
+		checked: 455, 526, 16, 16
+		checked-disabled: 474, 526, 16, 16
+		unchecked: 0, 0, 0, 0 # Empty placeholder to appease the missing-sprite-exception gods.

mods/modcontent/content.yaml

@@ -264,7 +264,11 @@ Background@SOURCE_INSTALL_PANEL:
 									Width: PARENT_RIGHT
 									Height: 1
 									Background: panel-rule
-						Label@LIST_TEMPLATE:
+						Label@LABEL_LIST_TEMPLATE:
+							X: 6
+							Width: PARENT_RIGHT - 16
+							Height: 23
+						Checkbox@CHECKBOX_LIST_TEMPLATE:
 							X: 6
 							Width: PARENT_RIGHT - 16
 							Height: 23