admin: add nick command for admins.

22:26 < clem1> rooooooooooo: nick dadokoakd
22:26 -!- rooooooooooo is now known as dadokoakd
22:26 < clem1> dadokoakd: nick kdoakdoas
22:26 -!- dadokoakd is now known as kdoakdoas
22:26 < clem1> dadokoakd: nick 
22:26 -!- kdoakdoas is now known as kdoakdoksoadk
...
22:27 < clem1> rooooooooooo: nick clem1
22:27 -!- rooooooooooo is now known as clem1_