Exact initial image

[stephenwf]

A new property on canvas panel and image service components to determine what the full initial image region is and make an exact pixel-perfect request for the initial load.

  <canvas-panel
    preset="responsive"
    canvas-id="https://digirati-co-uk.github.io/wunder/canvases/0"
    manifest-id="https://digirati-co-uk.github.io/wunder.json"
    region="466,2221,1612,450"
    exact-initial-image="true">
  </canvas-panel>

Whether the region is full, or a specific region, exact-initial-size forces CP to make just one request - or one request per image, if the canvas has multiple images on it. And then, only if it can - e.g., if level0 tiles only, it has to ignore this property (usually).

CP calculates its pixel w,h #147
Can it make a single request?
If so, do so, ignoring tiles, sizes and virtual sizes.