Structured QN update.
For LBFGS, first naive implementation, could expand formulae a little
bit to avoid substraction errors.
Merge branch 'struct-qn-mergein' into auglag-QN

Conflicts:
	nlpy/optimize/solvers/auglag2.py
Bugfix to store correct gradient in sbmin; change size of stored matrix in auglag drivers.
Removed exception for failed BQP line search. Small changes to structured SBMIN solver.