[IMPROVED] User payout estimations

* [ADDED] Proper PPS caclulations to statistics getUserEstimates
* [IMPROVED] Updated themes to use new estimates format in global smarty
* [IMPROVED] Updated PPS Dashboard to update estimates via Ajax
* [IMPROVED] Added PPS estimates to getdashboarddata API

This will require theme updates for those sites relying on the
est_<value> format for user payout estimates!

Fixes #743 once merged.
Merge pull request #763 from TheSerapher/issue-743

[IMPROVED] User payout estimations