Issue #306: Layout generator optimization. (dismine/valentina)

New issue 306: Layout generator optimization. https://bitbucket.org/valentinateam/valentina/issue/306/layout-generator-optimization

Roman Telezhinskyi:

For optimization time creation a layout for long sheets of paper (rolls) better will be cut them on pieces. Before cutting calculate max length we need for arrange details. It is longest side of the biggest detail. After creation unite pieces in one roll.