Overcome Gedcom.getSubmitter()

[michelesalvador]

Gedcom.getSubmitter() always returns the first submitter, and has now been replaced by Header.getSubmitter(Gedcom), that returns the correct submitter, which is not necessarily the first one.

I think there is still something to do about the task of multiple submitters:

• [x] Method Gedcom.getSubmitter() should be removed, or at least deprecated.
• [x] In Header there are a couple of comments recommending to use Gedcom.getSubmitter, and they should be removed.

[stoicflame]

Fair enough. I'm happy to merge a pull request.