add support for partition distribution

[jmspring]

EventProcessorHost which is documented here:

http://msdn.microsoft.com/en-us/library/microsoft.servicebus.messaging.eventprocessorhost(v=azure.95).aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-1

Allows multiple event processors to join and share the processing of partitions.

[jmspring]

One approach could be to introduce something comparable to the PartitionManagerOptions discussed here:

http://msdn.microsoft.com/en-us/library/microsoft.servicebus.messaging.partitionmanageroptions(v=azure.95).aspx

[noodlefrenzy]

EventProcessorHost uses blob leases, which are exposed in the storage API for Node so we could do something similar. They store the following information in the blobs:

An overall file - "eventhub.info" - containing a record like:
{"EventHubPath":"milanz-interop","CreatedAt":"2015-01-20T22:55:02.337Z","PartitionCount":16}

A directory/container for the consumer group (e.g. $Default), containing one blob/file per partition, named with the partition name (e.g. "0") and containing a record like:
{"PartitionId":"0","Owner":null,"Token":null,"Epoch":12,"Offset":"600","SequenceNumber":0}