Added support for a scrollable area in the dive info dialog

This patch puts the contents of the dive edit dialog inside
a scroll container, with a minimal size equal to the default dialog
size when no equipment is added. If more tanks and weights entries
are added, a scrollbar will appear on the right and the dialog
will become scrollable.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>