Add default options for a, b, c, d questions

[dsmith-unbc]

While running actel's explore, migration, or residency functions, user interactions are required for rendering any movement event or detections invalid. These require the user to select a, b, c, or d and if no input is selected b becomes the default option.

My suggestion is to add the ability to change b being the default option and instead of waiting for input, actel just selects what new input it has been given as default. For example, the option c for "detections before release" allows orphans to be discarded and then continue as normal. This could be preferable instead of default option b where it just continues as normal.

This change would be useful when running actel on remote servers such as those from Compute Canada where user interaction is not possible once the code has started running.