Add exposure protection tracking

Add exposure protection tracking

For simplicity and shortness, throughout subsurface exposure protection is
simply referred to as "suit".

Add the fields to the data structures, add the column to the dive_list
and the preferences dialog (once again with it being turned invisible by
default). Support loading and saving of the suit information.

Display the suit information in the Dive Info pane (this may be a bit
controversial as people could argue this should be in the Equipment pane)
and allow editing of the suit info, with our usual support for completion
and drop down lists to pick from.

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