Target image pane including warp, self targeting, and live camera

[joyhughes]

Related to #241, #246 and #72

For scenes with a target image, include an image picker with live camera and self targeting options, and possible warp fields below.

[joyhughes]

Instead of using this code:

    const targetImageGroup = activeGroups.find(group =>
        group.name === 'TARGET_IMAGE_GROUP' ||
        group.name === 'target' ||
        group.name.toLowerCase().includes('target')
    );

Add "target" to the options for tool field in menu (along with "pull-down", "image", etc.)

Below image picker in target panel include widgets defined in scene file - these can include warps and other effects (e.g. HSV color rotate) that can be applied to target image.