ENH: make sourceInfo sub-dictionary optional for topoSet (#1060)

- helps reduce clutter in the topoSetDict files.

  Caveats when using this.

  The older specification styles using "name" will conflict with the
  set name. Eg,

    {
        name    f0
        type    faceSet;
        action  add;
        source  patchToFace;
        sourceInfo
        {
            name   inlet;
        }
    }

    would flattened to the following
    {
        name    f0
        type    faceSet;
        action  add;
        source  patchToFace;
        name   inlet;
    }
    which overwrites the "name" used for the faceSet.

    The solution is to use the updated syntax:

    {
        name    f0
        type    faceSet;
        action  add;
        source  patchToFace;
        patch   inlet;
    }