Seperate Banners from Code

This pull request takes the existing banner code, tightens it up slightly, and pulls the banners themselves into a subdir for data.

This should allow future banner writers to at least not mess around with double escapes, and makes each banner atomic.

Also, this addresses a request to add a short URL to some of the banners so msfconsole users can at least hear about Metasploit Community, Express, and Pro.

[PT #41793473]
[FixRM #7716]