Planner: start the ascend with the strongest allowed deco mix.

In analyze_gaslist() we were only keeping gases that had their .depth
above the current depth, i.e. where we could switch to in the future. Now
we take note as well of the strongest gas that we could have already
switched to and switch to it before we attempt to ascend.

[Dirk Hohndel: minor whitespace and code cleanup]

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: make sure all cylinders have a sane depth

When copying cylinders from an existing dive, the mod of the cylinder
might not be set. Assume a conservative 1.4 pO2 and fill in those data.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: after freeing the plan, throw away the pointer

Otherwise we'll happily go back and access the freed data structures
later. Oops.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Planner: remove pointless code

This never made any sense. If we have NO datapoints then go and cancel the
plan? And anyway, we already check this higher up in the call stack.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Create Dive Computer configuration dialog

Create a dialog for reading and writing settings to and
from dive computers, with a menu entry in MainWindow to
open the dialog.

I will build up on this dialog and change it as needed.

Signed-off-by: Joseph W. Joshua <joejoshw@gmail.com>
Load vendor list and product list

Using code from 'downloadfromdivecomputer' class, this code
loads the vendors and products to the respective comboboxes.

Signed-off-by: Joseph W. Joshua <joejoshw@gmail.com>
Read basic details from dive computer

Added classes for reading data from dive computer. This is
at the basic level and I will expand it as I go along.

Signed-off-by: Joseph W. Joshua <joejoshw@gmail.com>
Create class to write settings to dive computer

Adds a class to write settings to dive computer, and modifies
the existing ones to integrate it.

Signed-off-by: Joseph W. Joshua <joejoshw@gmail.com>