Modify entries import to defer import of entries with origin

[ryanmitchell]

This PR fixes issue #75 by importing entries with no origin before importing items that do have an origin.

Fixes: #75

[what-the-diff]

• The code was refactored to separate entries with origin from those without.
• A progress bar is now shown for each group of entries (with and without origin).
• An info message is displayed before importing the localized entries, if there are any such ones in the first place.