Provide Export options in the UI

Ideas of options to support in a first version:

• TOC (at beginning of doc, after title page) (checked by default)
• list of figures (at the beginning, unchecked by default)
• list of tables (at the beginning, after list of figures - unchecked by default)
• whether pages should be numbered or not (checked by default)
• the document type (book or article in the first version)
• whether a header should be printed (will use a default template)
• whether a footer should be printed (will use a default template). Page numbering would go in the footer by default
• whether there should be a cover page or not
• let the user be able to enter: title, subtitle, author and date (they would be filled with default values)