change Page.element_types ordering /most-used at top
change Page.element_types ordering /most-used at top

Page.element_types returns the list of Page Embeddables
displayed in the 'plus' menu for a Page.

Now the first eight Page elements reference these 
models.

    Xhtml,
    OpenResponse,
    MultipleChoice,
    DataTable,
    DrawingTool,
    DataCollector,
    LabBookSnapshot,
    InnerPage,

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