Issue #292: Create 'Export Pattern' dialog. (dismine/valentina)

New issue 292: Create ‘Export Pattern’ dialog. https://bitbucket.org/valentinateam/valentina/issue/292/create-export-pattern-dialog

Susan Spencer:

Create an ‘Export Pattern’ dialog similar to the current ‘Save As’ dialog in Layout mode.

The user selects path, paper size, and file format.

When save is complete, the path and file name are displayed

For printable files, the message ‘Your file can now be printed’ appears. For 3D files, the message ‘Your file can now be imported into a 3D graphics tool, e.g. Blender’ appears.