Updated website address in NEWS.
Fix indexing mixed strategy profile of strategic restriction

In Python, when indexing a mixed strategy profile in a strategic
restriction by a strategy, the index of the strategy on the original
unrestricted game was being used instead of the index on the
restriction.  This revision corrects this bug.
Add support for writing strategic restriction to .nfg files

Being able to write a strategic restriction to .nfg files is essential
for using the equilibrium computation tools.  This implements this for
the underlying C++ StrategySupport, and for the Python
StrategicRestriction concept.
Bug fix in tracing strategic QRE on non-full supports.

The calcuation of function evaluations and Jacobians in strategic
QRE were incorrect in the case when the strategy profile does not
have full support.

In addition to correcting this bug, this introduces an implementation
of a player relative to a strategy support, which matches in part the
interface to the general GamePlayerRep.  This anticipates the eventual
introduction of strategic restrictions of a game, which currently are
only implemented in Python.
Fix bug in reference counting pure strategy profiles.

PureStrategyProfile had been reimplemented as a std::auto_ptr to an
internal representation class.  This was not correct vis-a-vis how this
class is used, as assigning a profile to another profile is assumed
to have copy semantics.  With an auto_ptr, these assignments were instead
transfering the internal representation pointer, leading to null
pointer dereferencing errors.  This was primarily observed in the
graphical interface, when editing strategic games after adding
strategies, but could also be triggered elsewhere.
Update version number to 13.1.1.
Merge branch 'maint13' after release of version 13.1.1.