Enabled frame unregistration

Enabled frame unregistration

Addons that are registering using ClickCastFrames should run
ClickCastFrames[frame] = nil or ClickCastFrames[frame] = false.

Addons that are using the group header, and are registering using
the secure snippet method should do the following:

local header = self:GetFrameref("clickcast_header")
header:SetAttribute("clickcast_button", button)
header:RunAttribute("clickcast_unregister")

This code expect to be run on the header, but needs access to the
button. This can probably be passed into your header via a frame
reference, i.e:

MyGroupHeader:SetFrameRef("foo", MyGroupHeaderUnitButton1)
MyGroupHeader:Execute[[
  local button = self:GetFrameRef("foo");
  local header = self:GetFrameRef("clickcast_header")
  header:SetAttribute("clickcast_button", button)
  header:RunAttribute("clickcast_unregister")
]]