Add multiple roles selection feature under article's contributors

[amruelama]

Add multiple roles selection feature under article>contributor as implemented under person>relationship (Issue #528) as most of the contributors are added via article page.

[lomky]

@amruelama this should be working on dev now. Let me know if it looks right!

It should actually work for every Object that has a "contributors" edit tab. e.g. figures, tables, articles, reports, etc.

[amruelama]

@lomky This works perfectly. But this also conflicts with issue #515. Is it possible to make 'author' the default role and also multiple role selection possible?

[lomky]

@amruelama great catch! I think it should work properly now. Pushed fixes to dev.