Spoon CompilationUnit improvements

[pvojtechovsky]

This issue is related to #1785

Sniper mode printer needs to handle package reference , import x.y.z; and list of types of compilation unit.
It brings several requirements on compilation unit.

• The compilation unit should implement SourcePositionHolder so it may act as root of the tree of source fragments (see review: feat: CompilationUnit extends SourcePositionHolder #2255)
• The compilation unit should have new property CtPackageDeclaration packageDeclaration
• packageDeclaration should hold SourcePosition of the line package x.y.z;. (see fix: CtPackageDeclaration position doesn't include top file comment #2811)
• CtCompilationUnitImpl#declaredTypeRefs should be declared as @MetamodelPropertyField(DECLARED_TYPE_REF) ... including @PropertyGetter and @PropertySetter on interface and appropriate RoleHandler
• CtCompilationUnitImpl#imports should be declared as @MetamodelPropertyField(DECLARED_IMPORT) ... including @PropertyGetter and @PropertySetter on interface and appropriate RoleHandler
• CtCompilationUnitImpl#packageDeclaration should be declared as @MetamodelPropertyField(PACKAGE_DECLARATION) ... including @PropertyGetter and @PropertySetter on interface and appropriate RoleHandler
• CtCompilationUnit should implement CtElement (which extends CtVisitable) and CtScanner should visit package reference, imports and all declared type references.
• CtImport.getParent() should return instance of CompilationUnit (therefore it must extend CtElement)

Concept related to Spoon AST model
CtCompilationUnit is not accessible from CtModel. It is not part of it's parent/child tree.
Each CtCompilationUnit is a root of own model, which has no parent, and has these children:

• package reference
• module reference
• imports
• references to included types.

WDYT? Do you see any problem? Drop here a note if you would have time to implement some part of that.

[tdurieux]

CompilationUnit should implement CtElement is a big change, and kind of broke the tree representation of the AST. Honestly, I don't fully understand the impact that this change can have on existing clients.

But I think it is important.

It also solves an issue that we have with comments, such as license, that should be associated with the compilation unit and not really with a class.

For the moment, I don't see problem.

[pvojtechovsky]

Last changes suggested here were merged in last days. So I am closing this issue.