refactor: Javadoc can be managed through JDT

Spoon currently manage all comments the same way, using `JDTCommentBuilder`, even if it's a source code comment or a javadoc comment.

However `JDTCommentBuilder` still have some bugs and is not created to manage - for example - Javadoc `@see` tags related to external types.
On the other hand, JDT which we are using to build the model already gives information about the javadoc and propose its own visitor for that.

So I propose that we move the creation of the Javadoc comment from the JDTCommentBuilder to the JDTTreeBuilder using the JDT visitor. The idea would be then to also get more information from Javadoc elements like the `@see` tags.

WDYT?