* Based PPLNS on Prop Payout script
* Using defaults from prop payout, no class adjustments
* Added more methods required for PPLNS
* Added block methods for dynamic payout calculations
* Added PPLNS Sidebar that also displays the PPLNS Target
* Shares beyond this target will not be included in payouts
* Shares missing to this target will be added from archives
* Enabled archiving by default for PPLNS
* Added configuration options for PPLNS
* Documented the usage for PPLNS, defaults are sane
* Added pplns_payout to run-crons
Addresses #143 and if accepted will fix it