When exporting to XML and no extension given, default to .ssrf

See #646

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Give Subsurface a distinct User Agent string

When accessing websites (divelogs.de, subsurface website) we shouldn't
pretend to be Mozilla 5.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: data base -> database

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: Reasoning for importing dives from other log books

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: Delete photo, Dropbox access

Text and an image were changed in order to reflect the
removal of images from the dive profile.

The text concerning Dropbox acces was reorganised.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: misplaced text.

Some of the text dealing with Dropbox acces was misplaced
(Thank you, Salva)

This corrects that issue.

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Latest translations from Transifex

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>