Constraints: Make phenotypes constrainable

* Decoders produce constraints on phenotype to inform other decoders
  about restrictions generated by decoders executed earlier in the
  process.
* Let the PhenotypeBase class implement the IConstrainedEncoding Iface
  such that all standard phenotypes are constrainable. Note that the
  Phenotype interface is not altered to allow the construction of
  unconstrainable Phenotypes.

Issue-Ref: 3279
Issue-Url: https://af3-developer.fortiss.org/issues/3279


Signed-off-by: Alexander Diewald <diewald@fortiss.org>