Move min/max committable age checks and input commitment check from filter to syntactical block validation

[jonastheis]

• make sure that the checks actually test the correct thing: a minCommittableAge=1 means that we can commit to a slot 10 once the first block in 12 has been accepted. This needs to be taken into account as such.
• verify that commitments are correctly set according to the syntactical validation rules in the BlockIssuer's getCommitment function