Generate scale bar

[james-rae]

• Requires issue Create setupMap function in mapManager #15 to be completed first. See that issue for detail on files & functions involved
• Having configuration schema finalized will be very helpful prior to starting this.
• Functionality will generate an ESRI Scalebar and apply it to the map (supplied by parameter)
• Any additional parameters for scale bar (to be determined when config schema is complete) should be applied (e.g. screen placement, metric vs imperial units?).