Consider change some const string to static readonly string

[Cologler]

Based on some articles:

• https://stackoverflow.com/questions/755685/static-readonly-vs-const
• https://stackoverflow.com/questions/3190870/const-string-vs-static-readonly-string-in-c-sharp

If any package has not to recompile, we may get the wrong information. For example, if the main process tries to read the version string from a hotfix dll file, it will always read the wrong value.

[kzu]

Yep, sounds reasonable. Created #64 to track its implementation.

Thanks!