Create a constructor with default parameters for some structs

Structs and classes in C++ are basically the same thing and we want to
create a few zero-initialized values for some of them; Sadly, C++ doesn't
have the nice static struct initialization that C has.

One way to deal with that is to create a constructor and pass default
values to it, another is lambda-initialization, but we don't use C++11,
yet.

Since we initializate stuff on the constructor, we don't need to
re-initializate things again on the initialization list (which is also why
I removed the QStrings from the initialization lists, they are
automatically initialized to empty)

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

subsurface-core/devicedetails.h

@@ -10,11 +10,13 @@ struct gas {
 	unsigned char helium;
 	unsigned char type;
 	unsigned char depth;
+	gas(unsigned char oxygen = 0, unsigned char helium = 0, unsigned char type = 0, unsigned char depth = 0);
 };
 
 struct setpoint {
 	unsigned char sp;
 	unsigned char depth;
+	setpoint(unsigned char sp = 0, unsigned char depth = 0);
 };
 
 class DeviceDetails : public QObject