Trial for the share over-report fix
Try to sniff out potential over-reporting of shares edge case
A couple stats improvements and re-add of time jitter on share submission checks

* Jitter is now subtracted when comparing last_graph_submit to current time instead of changing last graph submit
* Stale, duplicate, and low diff percentages are now shown in main stats
* User hashrate is now correct, and labeled to help show scale
* User share acceptance counts are now corrected
Fix for stupid 2.7 float issues
Half way done migrating the main data structures as a singleton
Quick proof of concept for signal driven block notifications