Added Line.compare(IgnoreCase), tests.
Added sort-lines, sort-paragraph.

I love it when abstractions come together to allow a whole bunch of work to be
accomplished with something so little incidental complexity:

    val r = Region(start, buffer.backward(end, 1))
    val lines = buffer.region(r)
    val sorted = lines.sorted(LineV.ordering)
    if (lines != sorted) buffer.replace(r, sorted)
    else editor.popStatus("Region already sorted.")