More robust share modal URL

[stevapple]

When working on #911 , I found that the URL construction logic in DocumentControlButtons is hard to say robust. It read the entire URL from window instead of internal states, and use string replacement for building latest version. Possible enhancements may include:

• Build URL based on internal states;
• Use version in URL if latest is not requested;
• Add an option to preserve URL query (see also Pass URL query to backend docs #912).