[Nickle] Nickle upgrades

[Barton C Massey]

The new Nickle argument parser has been debugged quite a
bit.  Still needs a real test suite and some documentation.

I added a Process namespace to the library, containing
implementations of system(), popen(), and a run_process()
that uses threads to support both input and output to the
same child process.  Also needs testing and documentation.

Next up: &&= and ||= assignment operators.  I have most of
it done, but I need Keithp's help to finish the compilation.

Have fun.

    Bart