This patch substitutes by isAttachedToDocument() (almost) everywhere where
getNameInDocument() is used for this purpose.
The very few places not touched by this patch demand a (just a little) less trivial change.
When we change the returning type of getNameInDocument() to std::string,
those places will be easily found, because they shall generate a compiler error
(converting std::string to bool).
Rationale:
The fact that getNameInDocument() return nullptr to indicate
that the object is not attached to a document is responsible for lots of bugs
where the developer does not check for "nullptr".
The idea is to eliminate all those uses of getNameInDocument() and, in the near future,
make getNameInDocument() return always a valid std::string.
Replace the int of the 'resolve' argument of several functions with a proper enum class.
* This avoids the inconsistencies in client code where often true/false is passed when an int is expected
* This avoids the use of magic numbers like 0, 1, 2 or the undocumented 3
Support sub-object in ActiveObjectList. This means that it can now
distinguish the same object being activated under different parent,
which may be in a different document through external linking.
