Replace System.Data.OracleClient with Oracle Data Provider Managed Driver

[tsahi]

Is your feature request related to a problem? Please describe.
System.Data.OracleClient is deprecated and won't receive updates. While this is true for the entire .NET Framework at this time, it also means no updates in .NET Core either.

Describe the solution you'd like
We should instead use Oracle.ManagedDataAccess. This might also help us with 32bit/64bit compatibility issues I'm facing right now.
And then, we need to remove the [Obsolete] attribute from the OracleDatabase and related classes.

Describe alternatives you've considered
There is also the unmanaged driver, which binds directly to the Oracle client library. but this is not cross-platform.

Additional context
We need to see if this package supports .NET Standard. There is also a separate package for .NET Core.

[tsahi]

To prevent a dependency on Oracle.ManagedDataAccess in applications that use SQL Server, we need to refactor DAAB so that the Oracle support is optional with a separate NuGet package, that will depend on this package.

[tsahi]

this will most likely fix #12