add Wpf and improve API for all UI frameworks

[VincentH-Net]

• WinUI and Uno Platform: changed namespace Microsoft.UI.Markup to CSharpMarkup.WinUI

• WPF: Add CSharpMarkup.WPF NuGet and CSharpMarkup.WPF.Examples application

• Improvements for all UI frameworks (WPF, WinUI 3 and Uno Platform):

  • Add many layout factory helpers generated via [ContentProperty] attribute
  • Add UIObject (and for WPF also UIDependencyObject) to allow specifying both markup and non-markup content objects without appending .UI
  • Add content parameter to the generated helper that has parameters for a view's self-defined writable properties
  • Add support for inheriting specified markup factory helper parameters in derived types, used for TimeLine
  • Add performant generic Spread() and SpreadS() (allocation-free)
  • Add .Resources() convenience helper
  • Add default bind properties for Brush derived types
  • Add implicit to.<Type> convertor from markup types to support e.g. .BorderBrush(Red)
  • Add generated to.<Type> type convertors from [TypeConvertor] attribute for WPF and UnoWinUI (WinUI does not use that attribute - need to select and add convertors manually)
  • Add support to use manual type convertors in codegen
  • Add 4 manual type convertors
  • Support passing in string and UIElement for Inline
  • Replace O<> with nullable value types to support automatic value conversion for builder helper method parameters, e.g. to compile Border(CornerRadius: 2.5). As a consequence remove redundant generated factory methods
  • Update and cleanup example applications
  • WPF example: automatic update on .NET Hot Reload

• Fixes