move startExport to DistortableCollection.Edit

[sashadev-sky]

Fixes #381 (<=== Add issue number here)

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[sashadev-sky]

@jywarren In #381 I should have moved startExport to DistortableCollection.Edit with the rest of the actions connected to the toolbar. Created a bug "startExport is not a function". This fixes that. bumping to 0.7.2 and merging because 0.7.1 has that bug

[sashadev-sky]

looping in @rexagod