[IMPROVE] Merged block statistics

* Removed 24 Hour Shares totals
* Expanded Block Overview with shares stats
[FIX] Use default cointarget if unset
[IMPROVE] Removed whitespace
Merge pull request #831 from TheSerapher/merge-blockstats

Merge blockstats
[IMPROVED] Cache active workers
Merge branch 'next' of https://github.com/TheSerapher/php-mpos into next
[FIX] PHP error due to worker change