Sage.app should use PATH set in .bash_profile

[iandrus]

A very common problem is that people don't understand how to set environment variables on OS X. This is because GUI applications don't inherit from a shell session and hence don't pick up changes in .bash_profile etc. It should be possible to have Sage.app (optionally) run a shell command which returns the (relevant?) environment variables from .profile and then put those in Sage.app's environment. Actually, it would probably be enough for the server starting script to source the user's .profile to pick up the changes since other uses go through a shell, though this would need to be checked.