The UI cannot be fully displayed on devices with large fonts

[KaiHuaDou]

I change the default system font size of Windows，and the UI cannot be fully displayed.

Explicitly set Width and Height and some configuration of RowDefintions/ColmunDefintions will occur this.

This problem can also be founded at other place in PixiEditor.

This might be a incomplete fix: https://github.com/KaiHuaDou/ColorPicker