Associate index with watchpoint for easy reference #14
Description
Right now the watchpoint index is based on its location within the vector. However, if we delete in the middle, that index can change. We can either assign an index when we create the watchpoint and use that when we list or print the watchpoint. However, that means we have to find it in the vector. We could also just mark "unwatch" vars as invalid so that we can reuse that space (or ignore it) and then the index is the vector index and it does not change (current easiest approach). If we don't actually delete and just keep adding to the end then the vector will continue to grow. If we reuse in the middle then it means we need to search for next open spot every time. Lots of possibilities here.