Changed readinglist2pocket script to only add read items and to add a Pocket tag for 'reading_list'

Pocket's use of tags allows us to specifically tag items as coming from this script (IFTTT does a similar thing). Added this.

Also changed it to only add unread items from ReadingListReader.
Fix for odd error where certain bookmarks in the plist file didn't have the 'ReadingListNonSync' entries.

Used a tenerary operator for the archived and fetched variable assignments to fix unexpected errors.