Add support for CQP's "global constraint" checks

[Akron]

In CQP further constraints (introduced by ::) can be added to tokens that are not directly serialized in the QL. An example by Elena is adj:[pos = "ADJ."] :: adj < 500"; which will return all adjectives in the first 500 tokens of the corpus. Some of these constraints should already be serializable in Koral but are not yet implemented.