Make impossible to change dives while editing one.

This is to prevent loss of data, so if the user is editing something,
either cancel the edition or save it, to continue moving around on
the Dive List.  - Only the dive list is affected, user can still
play with the globe and the profile.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
While editing the left button is renamed to "OK" to accept the changes

This seemed more logical than keeping it as "edit" and basically having to
hit "edit" a second time in order to save a change.

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