Amend botnet migitation protection for #wikipedia-fr

Summary:
Quit messages should be customizable. One candidate in addition to "Excess Flood"
is "Max SendQ exceeded".

New registry key: protection.botnet.reasons, a list of flood quit reasons

Suggested by Pitareio.
20:04 < pitareio> ah oui, c'est pas toujours "Excess Flood" le quit message

Test Plan:

• Deploy on Daeghrefn
• Run sign:excessflood Razoa ~Razoa@137.10.27.109.rev.sfr.net * #wikipedia-fr "Max SendQ exceeded"
• Check a ban has been put: 20:23:27 -!- mode/#wikipedia-fr [+b *!*@137.10.27.109.rev.sfr.net] by Daeghrefn

Reviewers: dereckson

Differential Revision: http://devcentral.nasqueron.org/D32