Re-added hashrate calculation support.
Implemented hybrid-layer hashrate calculation support and needs to be tested. MPOS layer also needs to be worked (#407).
Removed SupportsShareStorage, SupportsBlockStorage, SupportsPaymentsStorage properties from IStorageLayer as they were not being used.
Moved config.json website:stats section to upper level and renamed as statistics - need to fix the code too.
Moved StatisticsConfig.cs out of WebServerConfig.cs.
JobTracker can now clean expired-jobs - fixes #359.
IJob has now Creationtime property.
Moved json-properties to IMiner.cs and IStratumMiner.cs from StartumMiner.cs.
Merge branch 'develop' of git://github.com/CoiniumServ/CoiniumServ into develop
Merge pull request #418 from raistlinthewiz/develop

hashrate calculation fix, job-tracker improvements