Added requiredContent definition to Alternative Text field.
Defined minimal requiredContent for Image2 widget.
Added requiredContent definition to hasCaption field in the Image2 dialog.
Added requiredContent definition to Alignment field.
Extended docs for requiredContent informing about the limitations.
Don't set alt attribute if disallowed.
Don't caption the image when figure/figcaption are disallowed.
Don't align the image when alignments are disallowed.
Don't display the resizer when width/height are disallowed.
Don't set width and height if attributes are disallowed.
Disable justify commands when image alignment is disable by ACF.