Remove the Edit Saved Item Rectangles menu item in favour of a toolbar button.

The limit of 3 saved item rectangles has been removed - you can now add as many as you want.
However, the 1 per town limit is now strictly enforced.

The saved item rectangle is now shown with a cyan border when editing town.

rsrc/schemas/readme.md

@@ -180,7 +180,7 @@ in, as a point.
 sector.
 * `<on-init>` - Indicates the number of a scenario special node to call when the scenario
 first starts.
-* `<store-items>` - (max 3) Specifies a rectangle from which the player can retrieve items
+* `<store-items>` - (max unbounded) Specifies a rectangle from which the player can retrieve items
 after completing the scenario, as a rectangle with an extra `town` attribute that
 specifies which town the area
 * `<town-flag>` - (max 10) Specifies a rule to add the value of an SDF to a town upon

rsrc/schemas/scenario.xsd

@@ -189,7 +189,7 @@
 					<xs:attributeGroup ref="point"/>
 				</xs:complexType>
 			</xs:element>
-			<xs:element name="store-items" minOccurs="0" maxOccurs="3">
+			<xs:element name="store-items" minOccurs="0" maxOccurs="unbounded">
 				<xs:complexType>
 					<xs:attributeGroup ref="rect"/>
 					<xs:attribute name="town" type="xs:integer" use="required"/>