Add column generation initialization for VMAT dose mimicking

[sijiaww]

• Add column generation initialization for VMAT dose mimicking.
• Allow 'cg' as a valid initial_leaf_pos option in VMAT SCP.

[gourav3017]

@sijiaww Hi. Thank you for contributing. It looks good. Can you try to make change in the current version of the column generation code for vmat_optimization_col_gen.py for dose mimicking. You can refer vmat_scp_optimization.py. It have extra methods like create_cvxpy_intermediate_problem_prediction, run_sequential_cvx_algo_prediction for performing dose mimicking optimization. You can do the same for column generation. e.g. solve_rmp_prediction(), run_col_gen_algo_prediction(). This way we don't have to manage multiple files in future. Also I would suggest you to create pull request on dev branch always. It will be later moved to master branch after edits and further testing

[sijiaww]

Thanks for the suggestion, Gourav. I’ll proceed accordingly and will reach out if I have any questions.

[gourav3017]

Closed and created new pull request.