Milestone sage-3.0

GOALS:

• DOCTESTS: Raise the doctest coverage of the Sage library to 50%.
• INTERACT: Interactive versions of functions in the notebook; kind of like Mathematica's Manipulate command.
• R: a pexpect R interface
• TIMING/BENCHMARK: Making it so doctesting Sage also saves complete timing and profiling information. Start using and publishing the results of this.
• PORTING: gcc 4.3 support
• MODULAR ABELIAN VARIETIES: Implement Stein's algorithms for computing with modular abelian varieties. This is very *symbolic*, because Stein started the Sage project in the first place specifically to implement these algorithms.