ListViewColumnCollection Add methods now return the column object.
Added an IsResizeable property to ListViewColumns
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
Changed the text attribute api.
Removed unused text attributes.
Merge pull request #153 from mkrueger/listviewchanges

ListViewColumnCollection Add methods now return the column object.
Fixed null-ref exception when rendering Drawing/Figures demo [Win7 x64]
Added sorting to list view columns.
Merge pull request #160 from aBothe/pr

Fixed null-ref exception when rendering Drawing/Figures demo [Win7 x64]
Merge pull request #159 from hwthomas/master

[Drawing API] Add GetCTM to Context and update Transform code
Merge pull request #158 from mkrueger/master

Text attributes & coordinate transformation
Merge pull request #161 from mkrueger/listviewchanges

Added sorting to list view columns.