Additional features and bug fixes

[ritijain]

Change Description

• Added support for a DataTemplateSelector
• Added capability to compile the repository into a dll using asmdef.
• Added a GameObject extension to generate parent name hierarchy for easy debugging of bindings
• Improvements to DataContext editor experience in large projects by some additional error handling and performance improvements
• Added some editor support for cases where binding events added to the scene/prefabs at play mode don’t get cleaned up properly.
• Use system defined ObservableCollection and ICommand constructs when running player on a higher .net environment or in a UWP
• Add ability to pass custom parameters in ICommand implementations
• Added support to make sure backward compatibility with older unity versions does not break.

[ritijain]

@jbruening We have been actively using ugui-mvvm in some of our Mixed Reality projects at Microsoft, and we wanted to contribute back some of the changes we made in the process - add some functionality and performance improvements

[jbruening]

Wow thanks for the pull request! I'm glad you're finding the library useful.