sophie-package -- Package file format

[deyan]

• Package file format should be named "Sophie Package" and the extension should be .pack.s2
• A Sophie package should contain the book itself and the locally linked resources.
• The Sophie package should be a zip
• Open Package
• In the 'Export Book As' menu there will be a new 'Sophie Package...' sub menu which will export the current book to a pack.s2 format.
• There must be entry in the file menu "Open Sophie Package".
• When package is opened its contents should be extracted in the temp directory and the book should be opened, then when the user choose to save it, a dialog for choosing location should appear as if the book is new.
• Optional - a progress bar should show that Sophie is packing/unpacking.