- provide isBinary boolean parameter to addColumn function

- if isBinary true invoke setColumnBinary
- which should call set_binary() in a similar fashion to how SetColumnInteger called set_int()
- adding a binary constraint to a column is similar to setting an integer
- i.e. lp.addColumn('x', true) for integer variable can now be lp.addColumn('x', false, true) or lp.addColumn('x', true, true) for that matter