Simplify irssi hiera

To make your hiera data match, you need to convert the following into arrays by replacing the key with a "`-`":
* `irssi::bitlbee_nick_instances - accounts`
* `irssi::bitlbee_nick_instances - channels`
* `irssi::instances - channels`
* `irssi::instances - hilights`
* `irssi::instances - ignores`

Additionally,
* Convert `irssi::instances - chatnets` into an array by moving the chatnet key into the chatnet hash under the key "`name`".
* Remove the array-ness of `im::instances - chatnets - sasl_auth` - Keep the `password`, `type` and `username` keys, but remove the "`-`" in front of them.

Once you've done all that, you should see no change when you run puppet with `--noop`.