Eliminate duplicate gates in inbound list

[RickWieman]

The current implementation allows for duplicate gate proposals in the inbound list. In itself not a big deal, but it would be better to first find all real-life gates, and then find the random gates (leaving out the real-life ones). The random gates should also be unique.

Via Johan D.

[RickWieman]

This might require certain infrastructure changes. Perhaps it is better to automatically 'assign' all gates, and to let the user make changes if he really wants to. Could also be related to #8, as in that case, the randomly determined gates should always be the same.