Relative Panel Declaration Order Matters #430

Describe the bug
A clear and concise description of what the bug is.

<h:RelativePanel Background="White">
            <Rectangle Name="rect1" Height="10" Width="20" Fill="Red" h:RelativePanel.Below="rect2" />
            <Rectangle Name="rect2" Height="10" Width="10" Fill="Yellow" />
</h:RelativePanel>

does not produce the expected output.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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expected:

actual:

Environment (please complete the following information):

• .net: [e.g. 4.6.2]
• IDE [e.g. vs2017]
• Version [e.g. 1.0.0]

Additional context
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