Add interactive mode for adding books

**Is your feature request related to a problem? Please describe.**
Although passing commandline arguments for adding a book is nice for scripting, sometimes it might be more user friendly and comfortable to have an interactive mode to add information.

**Describe the solution you'd like**
A call like "booktrack-cli -l bib.json repl" should start an interactive mode in which the user is asked to enter the information about a book.

**Describe alternatives you've considered**
The interactive mode could be also available for editing books and all the other subcommands. Also it might be possible to start the interactive mode automatically when no commandline argument is given or something like that.