Revert unwanted changes potentially breaking wxGlade support.
Partly revert 34d4c77ccb1bcb14601ab347ec6080466b7e143d. Skips evaluator related changes that was included by mistake.
Re-using elements with Inkscape clones (svg:use)
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Re-use of pages
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Re-use of widgets
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Re-use of SVG elements in widgets
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