opennet: increase maxpeers to 140

--HG--
extra : amend_source : ed3b947966c6da40791630e2fc144e62934e5767
opennet manager: clearer comment

Replaced the imagined distance level by the simple hop. The imagined
distance level referred to a simplistic network model with several
stages of link lengths instead of the more organic link building
freenet uses. It did not help understanding.