Add ability to input to load data from client

[Roman Simakov]

I guess it's possible if INPUT will have an ability to request data chunks from the client library. Client library will have handler of chunk requests and send to coordinator. When coordinator get it it will store chunk and signal INPUT ARRAY to catch it.

This improvement allow us to load data to cluster from clients directly without the need to copy data to coordinator.

I suggest to add -3 as predefined constant for such mode of work. If the code will not really correlated to INPUT ARRAY operator, it makes sense to separate it in new operator.