Change name of TransformedSource during construction

[tischi]

Hi @tpietzsch @axtimwalde @tinevez, (cc @NicoKiaru)

It would be very useful for me if I could change the name of a Source when transforming it.

I would thus like to add constructors to TransformedSource that accept a String name.

And then I would change:

    @Override
    public String getName()
    {
        return source.getName();
    }

to

    @Override
    public String getName()
    {
        if ( name != null ) return name;
        else return source.getName();
    }

Would you accept a PR that does that?

[tpietzsch]

closed via #127