Unify arguments to scatter and maplot; use text instead of testxy to gain more control over labl positions.

- scatter and maplot now take the same set of arguments for specifying report depth and for pulling out specific genes.
- test labels are not positioned closer to the point they label.
Allow scripts to be run from a directory other than R script dir; Unify arguments for scatter and maplot.

- Add a small fragment at the start of all scripts to identifying script directory and including morrislib.R from that directory.
- Make scatter abd maplot take the same set of command-line modifiers.