manualintegrate: handle unevaluated derivatives

Changes:

- `manualintegrate` can integrate derivatives, as requested in https://github.com/sympy/sympy/pull/2126#issuecomment-18769905

Examples:

    manualintegrate(pi * Derivative(x**2 + 2*x + 3), x) == \
        pi * ((x**2 + 2*x + 3))
    manualintegrate(Derivative(x**2 + 2*x + 3, y), x) == \
        x * Derivative(x**2 + 2*x + 3, y)
    manualintegrate(Derivative(sin(x), x, x, y, x), x) == \
        Derivative(sin(x), x, x, y)