Move method clock into a new interface, that way we can clock only things that can be clocked.
New method unlinkall()
API change, changing the name of some methods in sigproc and signode
Putting things into namespace dspunit
mimosystem::create now have a Func template argument

This new template argument is used to construct (in freestore) a new sigproc.
Defaults to calling new.

I'm not entirely satisfied with that however:
- there's some kind of repeating of the return type;
- it cannot use functors with state because it does not accept a functor argument.

We'll see if I find a way to work around these.
Now the things use typedefs for clock and signal values.