fixed mongo raw query parsing
small DocumentContract.ExtensionValues null checks
added http handlers for services
IHttpService renamed to HttpService class and added CurrentUser property
CORS handler moved to an IHttpHandler implementation
added SessionTokenHttpHandler for http basic auth and AccoutnSessionHttpHandler for mongo user checks
better http exception handling
Merge branch 'feature/authentication'

* feature/authentication:
  added http handlers for services IHttpService renamed to HttpService class and added CurrentUser property CORS handler moved to an IHttpHandler implementation added SessionTokenHttpHandler for http basic auth and AccoutnSessionHttpHandler for mongo user checks better http exception handling
  small DocumentContract.ExtensionValues null checks
  fixed mongo raw query parsing