Contribute by Joseph Vallender <joseph.vallender@siftmedia.co.uk>

A few variables names got lost when moving between 6 and 7 syntax, which
cause the box ratio to stop working. Crop area seemed to be used for
cropping and resolution - I have separated these out now.

Also, I have re-introduced the 'Enforce minimum crop size based on the
output size' setting which is needed for all combinations of settings to
work correctly.