Remove explicitly copied dependencies, copy entire solution
into the conainter and depends on the cache to reduce build
time.

Addd temporary solution file which does not contains the
dcproj file to work around the issue that the dotnet cli
cannot handle dcproj.

Fixed issue #419

Removed Sessions in WebMVC app
Fixed GracePeriodMgr issues using multiple instances

1. Changes the build context of all services to the root level to be
able to access the dependencies for each project.
2. Commented out the prepublish scripts, these steps are moved into the
Dockerfile

Did not change any script yet, need help to identify what scripts we
need to change.

The new class BackgroundService is compatible with the current IHostedService interface in .NET Core 2.0.
I removed the similar but nont-tested HostedService base class (it was not official from the .NET team) that we were previously using.