Transactions, PPS Payout and Site Template

This merge should add the PPS Payout to the crons. Details on the current cron Workflow can be found on the WIKI (soon (TM)).

* Renamed ledger to transactions class
* Removed ledger cronjob, we use block references for direct confirmations
* Renamed sharecounter to pps_payout cron
* Store accounted shares in statistics table