Sort out javadoc content and clear 404 errors

[nmarquesin]

Issue Title

Sort out javadoc content and clear 404 errors.

Describe the bug

Sort out javadoc content: TotalCross javadoc today includes both tc.* and totalcross.* packages. I understand that separating the SDK doc from the converter & packaging doc could improve understanding both for users and contributors, as well as being a step forward in improving documentation.

Clear 404 errors: selecting "All Classes" a large number of classes is displayed with "Sever Error 404 - file or directory not found". This makes for a poor experience when browsing the documentation, which we most certainly want to avoid ;)

The image below shows one instance of this error, but at least most of the classes named BC*_* have the same issue.

Additional context

Not applicable.