Sniff Response: Detect the browser type and capabilities category

This class can be used to detect the user browser type and its category based on expected capabilities.

The class analyzes the user agent string and depending on the detected browser type it can assign to one of 4 groups: not OK, just OK, modern, and unknown. The browser name and version is also detected.

This class can help generating pages according to the detected browser capabilities, like for instance: outputting warnings, generating crude HTML that is browser independent, etc.