Overhaul of OS fingerprinting with Recog support

This reimplements much of the OS fingerprinting within the Metasploit Framework. Client-side and server-side fingerprints can now take advantage of [Recog](https://github.com/rapid7/recog) and the Recog-enabled MDM gem. 

The changes are backwards-compatible, but they do change how os_name and os_flavor fields are handled. Previously, an OS match of "Windows XP" would be split into an os_name of "Windows" and an os_flavor of "XP". The new code would treat os_name as "Windows XP" and save os_flavor for the product edition (Home, Pro, etc). This change is cosmetic and mostly transparent given how most callers treat these fields (they merge them together for display).

Here and everywhere else where you are setting the value to something like an OS name, vendor, flavor or combination of them, why not use the constants?  That way when someone decides that it needs to be called something every-so-slightly different, you simply have to change the constant(s) rather than dozens of files that use the bare strings.