Add options for Zotero import

Add the following options in the configuration file for Zotero import from interactive CLI:

• Zotero -> attach_pdf (true/false): whether to attach the pdf file of the article to the Zotero item

  If true, the article is downloaded and attached to the Zotero item. If file sync is not activated in Zotero, it is necessary to also provide the path to the local Zotero database in Zotero -> local_database_path

• Zotero -> choose_collection (true/false): if true, prompt to choose another collection than the default one, with autocompletion for collections down to the first sub-collection level.