Started work on Weibull distribution of session length, and more

Added Apache Math library
Trials occur until statistically significant results are obtained
Download time (session length) is derived from Weibull distribution
Added Weibull sampling for arrival time

A random sample of nodes are now provided with an arrival time that
they decrement at each step. When their arrival time is 0 they become
active. Much like the availability time.
Fixed bug with every node searching on round 1

That was a silly mistake.
Added lots of println logging.
Fixed bug

Nodes were available for ever, not anymore.
Refactoring

Changed trialsRequired calculations.
Pulled requests_made and responses_received from Early_only