Fix for sample interval on Divelogs.de export

Logic when to use default sample interval was mixed.

Fixes #657

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
CSV import: add min:sec format support

On CSV import the time can be represented with seconds, min:sec or
hour:min:sec. This patch adds support for the min:sec format that was
missing.

See #662

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Don't mess with the selection when closing a file

Our core structures are kept consistent by calling delete_single_dive()
and there is no reason at all to even touch the UI selection as this all
goes away with cleanUpEmpty()

Fixes #660

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
User manual: Add section on dive log storage in the cloud using dropbox

Some other dive log programs present storage of dive logs on the Internet
as an important feature. Therefore this text.
One image was added.

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