[INFRA-146] - Move all configurations to a customizable IrcBotConfig

This PR is a slight overkill for INFRA-146, but such generalization could be useful for future testing purposes or "#jenkins-infra-admin"

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
`"name"` should presumably be `".name"` (or `varPrefix` should end with a dot).