* [ADDED] getUserMiningStats to fetch all speed related data
* Uses global cache if available, falls back to local query and then
local caches
* [REMOVED] getUserHashrate, getUserSharerate, getUserAvgShareDifficulty
* [UPDATED] All code occurences for the above to use the new system
Probably won't change much since global cache was already used but does
help on the Dashboard since we combine at least 2 calls into one.
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