Option to hide certain nicks [matrix -> irc]

[TomTheDragon]

Since we do use multiple bridge bots on the matrix side, it would be useful to be able to hide those bots in the user list on the IRC side, which would also free up a slot for an another user.
There is for example no need to show the telegram bridge bot on the IRC network.
An option where we can just drop a few names, should fix this problem.