User specified QDK package versions silently discarded in favor of latest version

[anjbur]

Describe the issue When loading a notebook with a .csproj (or if packages are loaded using the %package magic command), the versions for any QDK package listed are ignored in favor of the defaults in src/Tool/appsettings.json (see Workspace.cs#L399). This is done to ensure the most recent version of the Microsoft.Quantum.* packages are used, and to ensure the same version is used across all the packages. However, this is done without visibility to the user that their specified version is not being used. It also presents some difficulties in development that an alternate package version can't be easily loaded.

Desired behavior

• Add a message to the user in %workspace magic command (and in the logs) if their specified package versions are overridden.
• Allow a user to choose to load a specified package version instead of the default.