Update the KMIPProxy client to support batch processing

This change updates the KMIPProxy client to officially support
batch processing. Passing 'batch=True' to any operation method
will queue up the operation request. The entire queue will be
sent when 'batch=False' is passed to an operation method. Instead
of the single operation result, a list containing all operation
results will be returned.

Partially addresses #403

Author: PeterHamilton