Support gpz files

Similar to the gpx viewer app please also add gpz files support into Locus app.

An advantage is you don't need to change the extension anymore between both apps.

With a Locus direct app import both the zip and gpz files will deliver an equivalent result.

- A zip file is usually associated with your android unzipper app.

- A gpz file is so more comfortably associated with the preferred gps app.

Example file attached.