When recropping an already-cropped image, open the parent image with crop region preselected

When recropping an image that is already cropped, instead of showing the image itself in the crop interface, it would be useful to show the parent image instead - with the current crop region preselected on it. This makes it much easier to make small adjustments to an existing crop.

As a result of this change, the "Related Crops" interface becomes less important than it previously was, so this issue will also make it so that particular sites can configure that interface to be collapsed when the True Crop interface is open (by adding a new variable 'truecrop_expand_related_crops' that can be set to FALSE). However by default it will still be expanded, if that variable is not set.

This patch relies on #2810117: Pass the element that triggered the croptool to be opened to ManualCrop.showCroptool() and use it to ensure the correct croptool is opened for the Manual Crop module (and possibly others).