Allow a user to set a title for the process in the process tree.

Useful for finding a specific roundup-server process rather than looking through all
the python processes for the one that needs killing.

1) add -P <processname> to roundup-server
2) if setproctitle not installed exit with error
3) if installed call it after uid switched to normal user so setproctitle not called as root.

for roundup.cgi:

1) if env variable ROUNDUP_PROCESS_NAME is set, and secproctitle installed,
   call setproctitle with that name
2) if setproctitle not installed, just continue.

I think these are the only two frontends that can benefit from this. wsgi and zope
IIUC are both run by a parent process in an embedded interpreter. For wsi gunicorn the
--name option lets you name the process.