Working on handling UnallowedNegative exceptions that are popping
up. If a parameter goes to a unallowed value during differentiation,
it should now discard the forward and backward steps for that
parameter, change the step size to 0.05 * current parameter value,
and then try the differentiation again (hopefully without a
UnallowedNegative exception this time).
Pulls out coordinates from Gaussian logs.

Not used in Q2MM really, but it's a convenience thing.