New Session Instantiation

[Mike Cvet <mcvet at redhat dot com>]

An issue that has come up recently is that of a single user being able
to run multiple simultaneous session of Frysk.

Currently, a second invocation of Frysk when there is already a running
instance results in an error message printed to the terminal (or into
the abyss, if run from menu) informing the user that Frysk is already
running. The currently running session has its MainWindow brought to the
foreground.

Ideally at some future juncture, this will instead result in a new
session of Frysk being run by the same Frysk process. A somewhat more
detailed and graphical explanation can be found in this workflow on the
Frysk website: http://sourceware.org/frysk/workflow/new_sessions/

This will require a major refactor in the GUI code, since the vast
majority of current windows are static singletons - these will require
their own factories to be dynamically created. Furthermore, there are
likely other issues inherent with running multiple sessions at the same
time. 

There isn't yet a plan or timeframe for this move, but likely within the
next couple months.