Conversations can be "forked", to create a copy of a conversation at a given point. This allows e.g. prompting a conversation with a system prefix just once and then forking it again and again for each individual conversation. Conversations can also be "rewound" to an earlier state.

Added two new examples, demonstrating forking and rewinding.

- Removed special case for exit
 - Added a wait at the end of batched decoding

- Renamed files and updated namespaces in Examples folder.
- Moved files from NewVersion folder to Examples folder.
- Removed TestRunner.cs file.
- Updated Runner.cs to include new examples.
- Update Program.cs to use the new Runner class instead of NewVersionTestRunner
- Update LLama.Examples namespace in Program.cs
- Update await NewVersionTestRunner.Run() in Program.cs to await Runner.Run()