Improve the data protocol

There are many operations that require multiple requests being sent to server.Not only it decreases perfomance , but also it may cause race condition, when data is being changed between several operations. 
For example : when user wants to store the data it should first either check if item exists and based on the result set and create the record ( another option is to try either set or create first and if it fails try to second command ) 
Even more problematic op is delete. In case the node has many children, the application should remotely collect those nodes and then delete them. Same for getting children data. 

Therefore , in order to improve the perfomance following operations may be very valuable
1) createOrSet - in some case the goal is to store the value , and its prior state is not important

2) recursiveDelete - this operation actually exists in CLI but does not exists for remote commands

3) getChildrenData - return all nodes children together with their data.