Fix known issues, optimize user experience.

[xixihahaliu]

1. When the system command is missing, the download prompt is clearer.
2. Add lastset Updates to the readme.
3. Prompt the user whether the code repository is up to date, only for master branch.
4. Optimize the startup process, provide more detailed error information to prevent continuous output of 'waiting for coffee'.
5. Fix the bug that some models of graphics cards (such as v100) will prompt as unsupported when using the openai API.