Bouncing behaviour reworked

- The acceptance probability is now constant. Previously it was
  increased with every bounds. The behaviour now is an exponential
  cutoff, whereas previously another exponential factor was added by
  modifying the acceptance probability (exponentially).

- Bounces left and acceptance probability are now capped by the node's
  configuration. This prevents bad EdgeRequests with 'maxBound' bounces
  or acceptance probability 0 that clog up the network.