cleanup of callback/signal headers

removed old callback/signal headers
removed typedefs
added move constructor
add callbackcontainer as a replacement of slotcontainer
fixed const correctness in callback
finally fixed segfault in new callback class

I think the main error was to store a reference to the signal/callback.
Now I store a copy of it and everything works fine.
Also work on a copy in the invoke method (in signal) so you can safely
remove (disconnect) callbacks from the signal
replaced every occurrence of old signal/slot

The new callback/signal class is now totally integrated in the clanlib
sources. Only the examples and documentation is left over. Will be done
soon.