* Applied some code conventions, used more current language features which should improve readability and making it easier to re-factor / modify. Also fixed some typos in documentation.
* Changes based on PR conversation for the SystemInfo
* Some modifications due to conversations on the PR, especially I removed the FlagsAttribute on the BalloonFlags.
* Removed Silverlight targeting in code.
Add extension point CustomPopupPosition to show Balloon on custom position.
AppBarInfo.WorkArea now return appbar workarea. Before it returns screen workarea.