Remove ack_finder/ack_find_base

Remove ack_finder/ack_find_base

ADD_ACKNOWLEDGER and ADD_END_ACKNOWLEDGER can work without them when
the base is specified correctly when calling them inside of some
CLASS::boot ().


Also contains commits:

Let ADD_ACKNOWLEDGER state actual classes

Declaring the correct containing classes for acknowledgers
allows dropping a bunch of black magic.


Simplify ADD_{,END_}ACKNOWLEDGER

No explicit scopes are needed any more since they are run from within
the static member function CLASS::boot () .