Implements a 'Increment/Decrement Counter' CRDT, also called a 'PN-Counter'. It is described in the paper A comprehensive study of Convergent and Commutative Replicated Data Types. PN-Counters allow the counter to be incremented by tracking the increments (P) separate from the decrements (N). Both P and N are represented as two internal [[GCounter]]s. Merge is handled by merging the internal P and N counters. The value of the counter is the value of the P _counter minus the value of the N counter. This class is immutable, i.e. "modifying" methods return a new instance.

[SerializableAttribute]
public sealed class PNCounter : IReplicatedData<PNCounter>, 
	IReplicatedData, IRemovedNodePruning<PNCounter>, IReplicatedDataSerialization, IEquatable<PNCounter>

[<SealedAttribute>]
[<SerializableAttribute>]
type PNCounter =  
    class
        interface IReplicatedData<PNCounter>
        interface IReplicatedData
        interface IRemovedNodePruning<PNCounter>
        interface IReplicatedDataSerialization
        interface IEquatable<PNCounter>
    end