Mute Toggle Character Switch Notification

[mgeitz]

In hindsight, this was mostly put in for debugging purposes. Add a toggle-able mute option to work for the "Character changed to [char] on [server]" voice notification and any other older notifications which still cannot be toggled or otherwise muted in the options page / settings.yml to individually mute notifications like this - https://github.com/mgeitz/eqalert/blob/master/eqa/lib/action.py#L349

I wouldn't have realized this without seeing this change, thanks @bivouac598 🥇
bivouac598@ecfe32e#diff-0c08db649bda667203583bb8875548ff8d6fedcf603ce17876f5066a41705eb8R557

[mgeitz]

This would require being added to state out of settings.yml and really doesn't seem worth it with the current state structure - removed in #184