Exposed Global and Thread Contexts of NLog and Log4Net via Common.Logging
Added tests
Merge branch 'master' of github.com:meixger/common-logging into meixger-master
add links to new ***Context.cs files to additional logger implementations added since original fork was made for this work
add additional NLog *Context tests to additional NLog implementations added since initial fork was made for this PR
Merge branch 'meixger-master'