Improve signal handling

Ignore several UNIX signals we are likely to receive but that we
do not want to process. For SIGINT, send an explicit shutdown message
through our internal queue instead of relying on a KeyboardInterrupt
exception.

DHC-1918

Change-Id: I627d26ea4038801c8f4a59840e0042214d6beea6
Use shorter names for main proc. and thread

The default names, MainProcess and MainThread, are much longer than
the names we give the processes and threads we create. Use shorter
names that look more similar.

Change-Id: Idde69ff20a1b42b3e0524f0101daf64cabb6b721
Improve shutdown behavior

More work to handle cleaner shutdown on Ctrl-C, including
reporting status for any work that is going to be lost and
more detailed logging of the progress for shutdown.

Change-Id: I0a3d4a53fd76d4ad2b1aa0478adad349a4edffb7
pep8 fixes for 1.5.0

Yay, new rules!

Change-Id: Ic6a30ef0e8fa3d2337987b16160fa7e00b338a4b
Merge pull request #122 from dhellmann/feature/better-signal-handling

Improve signal handling