Move static variables to IrcBotConfig

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Fix channel handling logic.

Changes:
- Reconnect to all all channels after the disconnect
- Update users cache for a proper channel if user permissions are insufficient

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>