Added filesexist command

Added support for a global configuration.

See README for more details.

Fixed `move` command not updating the library properly.

Added `move` and `id` commands:

Move audio books to a new folder with the `move` command.
Find audio books that refer the given path with the `id` command.

Added the "details" command.

The command prints all available information for the given audio books
to the terminal.

Fixed exception when using unknown sort field names.

Updated filter options for the list command.

Fix for broken output.

Updated library format.

Added the option to sort output.