Updated Newtonsoft.Json 12.0.2

Updated changelog

Merge branch 'release/6.0.0-rc.1'

Merge branch 'release/6.0.0-rc.0'

Disabled PerformaceCounters in net45 tests, updated readme.

There are issues with performance counters initialization when tests are run by CI tools

Removed useless files

Removed now useless tools, updated ocmments on build.ps1

updated appveyor.yml

Merge pull request NEventStore#412 from kblooie/RemoveCommonDomain

Removed CommonDomain. Deleted old nuget files for mongo and raven