[WPF] Try using WPF rendering api
Merge remote-tracking branch 'origin/master' into visual-render
Fixes in the context backend. Added missing files.
Merge branch 'master' into visual-render

Conflicts:
	Xwt.WPF/Xwt.WPFBackend/ImageViewBackend.cs
[WPF] Refactor code in context backend
[WPF] Fix figure filling issue
Added coordinate calculation functions to text layout.
Added support for text layout attributes.
Added overload of GetIndexFromCoordinates that takes a point.
Merge branch 'textcoordinates'

Conflicts:
	Xwt.Gtk/Xwt.CairoBackend/CairoTextLayoutBackendHandler.cs
	Xwt.Gtk/Xwt.GtkBackend/TextLayoutBackendHandler.cs
	Xwt.Mac/Xwt.Mac/TextLayoutBackendHandler.cs
	Xwt.WPF/Xwt.WPFBackend/TextLayoutBackendHandler.cs
	Xwt/Xwt.Backends/TextLayoutBackendHandler.cs
	Xwt/Xwt.Drawing/TextLayout.cs
Implemented text layout memory management & pango byte index mapping.
Conflicts:
	Xwt.Gtk/Xwt.CairoBackend/CairoTextLayoutBackendHandler.cs
	Xwt.Gtk/Xwt.GtkBackend/TextLayoutBackendHandler.cs
	Xwt.Mac/Xwt.Mac/TextLayoutBackendHandler.cs
	Xwt.WPF/Xwt.WPFBackend/TextLayoutBackendHandler.cs
	Xwt/Xwt.Backends/TextLayoutBackendHandler.cs
	Xwt/Xwt.Drawing/TextLayout.cs
Implemented utf-8 mapping & all indices are now int instead of some
beeing uint.
Fixed drawing with gtk text backend.
Fixed text decorations
Changed GetExtendsFromIndex to GetCoordinateFromIndex.
Cleaner API & easier to implement in the mac backend
[Drawing API] Add GetCTM () to Context
Changed the text attribute api.
Removed unused text attributes.
Fixed null-ref exception when rendering Drawing/Figures demo [Win7 x64]
Added sorting to list view columns.