BUG: Make translatable Editor Effects titles in Segmentations

[mhdiop]

Enables fixing of these issues:

• Mark all user-visible strings as translatable in C++ SlicerLanguagePacks#12
• Some strings cannot be translated to other languages #6177

[lassoan]

This is very good, just added a few comments, mostly should be easy to fix.
The only topic that may need some more discussion is how to initialize the title (in the constructor).

[lassoan]

If you don't want to make effect title editable then remove this method.

[mhdiop]

This method is required by scripted effects so that their title property is writable.

[lassoan]

Suggested change

	Q_PROPERTY(QString title READ title WRITE setTitle)
	Q_PROPERTY(QString title READ title)

[lassoan]

Why Python and C++ effects behave differently? We should keep the behavior the same for both (either both required to set the title in the constructor or neither).

[mhdiop]

Why Python and C++ effects behave differently?

I made this to be coherent with the current definition of the class in which name and perSegment properties are meant, in C++ effects, to only be initialized from the constructor, not through a setter.

The different behaviour is justified by the fact that the setTitle method is required for scripted effects to make the title property writable (even in the constructor). What is not the case for C++ effects in which initialization may be done in constructors without using the setter.

I will however do what you suggest and keep the same setter's behaviour for all effects types. It should not be a problem since that property is not as critical as the name which is used in other contexts.

[pieper]

Yes, we want to keep the C++ and Python APIs as similar as possible to help people more easily go back and forth between languages.

[mhdiop]

Thank you for your feedback, that's what is done in the last submitted commit.
setTitle is now only defined in qSlicerSegmentEditorAbstractEffect base class and inherited by all other derived effect classes.

[lassoan]

Parent folder name is added to the context name is if the folder contains __init__.py. Since the folder structure is different in the source tree (where strings are extracted from) and the install tree (where strings are replaced at runtime), the context strings are different and therefore translation fails.

To resolve this, I'll reorganize the folder structure in the source tree to match the install tree. Do not merge until then.