Set PYTHONPATH so that scons can find saliweb package.
Set PYTHONPATH so that scons can find saliweb package.

In the new Ubuntu environment, scons uses /usr/bin/python, not the
virtualenv Python, so won't be able to find the saliweb package.
Help it out by setting PYTHONPATH.

salilab/allosmod,salilab/allosmod,salilab/allosmod,salilab/allosmod