Back out changes in r842 and restore damage meter registration.

Back out changes in r842 and restore damage meter registration.

OvaleFuture needs to send out messages to all of the registered
damage meters when a scored spell has been cast.

Improve the implementation of the registration so that it only
requires a function or a method name instead of the module itself.
This makes it easier for other damage meters to implement a small
function to receive score information from Ovale instead of
implementing a full-blown Ovale module.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@855 d5049fe3-3747-40f7-a4b5-f36d6801af5f