Add auto join on invite module

Join on invite module: Forces user to join specific channel on invite
Should be used with caution, as it allows potential abuse by users
Perfect when INVITE command is banned and reserved only to net admins
>void OnUserInvite(User* source,User* dest,Channel* channel, time_t timeout) CXX11_OVERRIDE

should be

void OnUserInvite(User* source, User* dest, Channel* channel, time_t timeout) CXX11_OVERRIDE

You could also consider omitting the names of the parameters you are not using e.g.

void OnUserInvite(User* source, User* dest, Channel* channel, time_t) CXX11_OVERRIDE