Fix bugs related to making Chrome default browser on Vista and also do some cleanup.
- Stupid bug where we were failing if there was a space or '-' in the path to setup.exe
- Some application still read default browser from Software\Classes\http even on Vista so set that
- Some refactoring of apppaths changes to make a method private that doesn't need to be public.
- Move constants in shell_util where rest of the shell related constants are.
- Remove duplicate attempts to create ChromeHTML key