rename absolute to abs
add QuadraticOp
add APolynomialOp base class
AFunctionOp base class
Move static Op instances to Ops class
widen default Op bounds to +/- infinity
add DerivativeOp
test derivative ops
derivatve op testing
SIN, COS, improve Op composition and tests
better compose for ops
warning tidy
more tests
Op products and compositions
warning fixes
fix derivative for ComposedOp