Fix Atlas/resolveConstraints for SNOPT student licenses.

Users with student licenses for SNOPT were getting "Maximum column size exceeded" errors when Atlas/resolveConstraints was called. `checkDependency('snopt')=1` in these cases, but the problem is too big for the limited license. 

Now, if the initial call to resolveConstraints fails, we try again using 'fmincon'.

Resolves #415