* Fix right aligned floating Watermark

* Use TextBoxHelper.Watermark for HotKeyBox
  instead own DependencyProperty
Allow AutoWatermark for HotKey DependencyProperty

* New TextBoxHelper.WatermarkTrimming attached property
  to set the text trimming behavior to employ when watermark overflows the content area.

* New TextBoxHelper.WatermarkWrapping attached property
  (only for TextBox) to set how the watermark should wrap text. Default is binded to TextWrapping property.

* Update 1.6.0.md