Replace naive matching algorithm

[abstxn]

The current matching algorithm tries to pop the oldest 2 match requests from the respective topic queue, and treats that as a match. Some enhancements can be made as discussed:

1. Not allowing for Easy and Hard difficulty match requests to be matched together
2. Having a priority queue that assigns priority as a function of request timestamp and difficulty
3. Popping multiple matches on each pass of the algorithm instead of just one at a time