external estimates of parameters

[kellijohnson-NOAA]

Create functionality within ss3sim to use sampled data to "externally estimate" parameters and place these in an EM as fixed values. We originally provided this capability for growth. I am removing this functionality with the update to 3.30.19 because I think that it should be included in the package in a more modular way and for more parameters. At any time developers will be able to roll the package back and see how we previously did this. A benefit of removing the functionality at the moment is users will no longer have to install {bbmle}. Please let me know immediately if you are using the external estimates of the vbgf in any current simulation so I can add it back in if needed. This issue will act as a reminder for future work that is needed not planned for immediate development.