SVGHMI: add support for "reference" and "frame" rectangles to spread-out ovelapping elements.

When HMI become complicated, designer needs to spread-out ovelapping elements
in order to unclutter drawing and facilitate maintenance.

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                  <xsd:element name="Linux">

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                    <xsd:complexType>

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                      %(toolchain_gcc)s

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                    </xsd:complexType>

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                  </xsd:element>