Fix: Image in related table

[steff-o]

Fixes #1757

Problem was that there was an asynchronous resize when the form is saved which messed up the current layer state variable.

Resolved by moving the resize to when the file is loaded (which in my opinion is more logical anyway). Previous implementation resized the image on save, which meant that the preview image was full resolution and the image was read twice.

The result should be the same which includes that the image is always resized to a max size of 600 pixels in the largest dimension. That can be overridden by setting a new max size by the undocumented maxSize option.

"attributes": [
        {
          "name": "name",
          "type": "text"
        },
        {
          "name": "imgsrc",
          "type": "image",
          "maxSize":  50
        }
      ]

[steff-o]

@leafisfalling, can you test this?

[Owemyr]

We have tested the image in related table fix, working fine, thanks.

[johnnyblasta]

Tested without related table and this fixes #1787 also.
Since it seems from two different parties that it solves when related table also, so it's good to merge then.

[jokd]

Agree, merge this