Dot-Bit.org's bitcoin/namecoin daemons crashed and were causing incorrect data.  Therefore they are no longer trustworthy.  Restoring BitInfoCharts as the hashrate source.  Also fixed the BitInfoCharts parsing.

Revert "Switched from BitInfoCharts.com to Dot-Bit.org as difficulty source."

This reverts commit af101fbaac52897cb76816cf0d72a2fa77010fc8.