"Enter" button activates default OK response.

Implemented for the following dialogs: Preferences,
Select Tags, Select Events, Renumber, Upload to divelogs.de

Not shure whether this is appropriare for Print and Planner
dialogs.

Signed-off-by: Sergey Starosek <sergey.starosek@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Hide user password in Upload to divelogs.de dialog

Signed-off-by: Sergey Starosek <sergey.starosek@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Initialize / reset selected_dive to -1

The value of 0 that we used is actually a valid value and could cause
confusion.

Suggested-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>