Serialization, bug fixes, and improved API

3.2.0.0

• Fixed show-cursor property when using render targets.
• Made Entity class abstract, since it makes no sense to instantiate it.
• Removed GetChildren(), added 'Children' property instead.
• Fixed bug with setting offset of dragged entities.
• Moved TabData outside of PanelTabs.
• Added Anchor and Offset public properties.
• Added PopulateDict function to convert tree to flat dictionary.
• Fixed Find<> with generic Entity type.
• Optimized processing multicolor text.
• Optimized stylesheet and memory usage.
• Created base panel class for better handling entities that are based on panels.
• Added way to change text input multiline mode.
• Extended dropdown and list API + added per-item-select events.
• Added serialize / deserialize functionality.