Fixing ElementName bindings in TransitioningContent

[Keboo]

Fixing name scope issue that would cause ElementName bindings to fail when used inside of a TransitioningContentBase.

Fixes #950

[SandaruwanFdo]

Is this fixed? I'am new to GitHub

[Keboo]

@proxact this is a pull request. So it is the first step into getting it fixed. The general flow looks like this:

1. Issue created in github.
2. Fix created in a pull request (this is the step we are currently at).
3. Pull request is reviewed and merged into the repository (this requires @ButchersBoy to do it)
4. NuGet package created with the latest code that contains the fix.

If you want to compile the library manually you can always check out my branch and build it manually.