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).

Why bare strings here (and earlier) but constants for Android?