Added methods to retrieve position and size from a GuiElement
Added draw() method with option to override hovered boolean to GuiElement interface and implemented it. This is required for GuiAdvancedButtons which would be tinted blue (as if hovered) even though an overlying GuiElement (e.g. GuiDropdown) was hovered
ComposedElement's entries are sorted so that GuiDropdown are always drawn on top
Modified thrown UnsupportedOperationExceptions in CustomImageObject to not be thrown if asset is null
Added enabled Field to DelegatingElement, which every instance can handle itself
Made isEnabled Field in GuiAdvancedTextField protected for subclasses to access
Made GuiDraggingNumberInput only draggable while enabled
Made GuiDropdown check enabled field before accepting mouse clicks
Properly tints GuiTexturedButton if disabled
