SVG export (#598)

* first draft of export to SVG. WIP

* enabled text rendeing - which is not quite right atm

* placeholder svg icon

* size the canvas based on the bounding box of elements

* Do not add opacity attributes if default

* render background rect

* Ensure arrows are in the same SVG group

* parse font-size from font

* export web fonts

* use fixed locations for fonts

* Rename export functions

* renamed export file

* oops broke the icon.

public/locales/en/translation.json

@@ -45,6 +45,7 @@
     "clearReset": "Clear the canvas & reset background color",
     "export": "Export",
     "exportToPng": "Export to PNG",
+    "exportToSvg": "Export to SVG",
     "copyToClipboard": "Copy to clipboard",
     "save": "Save",
     "load": "Load",