split SAGE_REPO variable into SAGE_REPO_ANONYMOUS and SAGE_REPO_AUTHENTICATED

Conflicts:
	src/sage/dev/git_interface.py
	src/sage/env.py
fix up some small issues with bdist/sdist
bit of cleanup with the upgrade process
deps: fix/remove some old references
sage-spkg: fix misleading message for `sage --info`
sage-spkg: update header comment to reflect current status of script