Revise the Update API for Segment definition

Description - 

The payload for patch call in the Update Segment Definition needs entire definition of the segment. It would be time taking and copy paste process to extract the definition of the segment and make the changes to the payload and resubmit as the patch. Instead, the patch solution should have been like Field Group "Patch" API call. Just what property we need to replace and the corresponding value. 

Why is this feature important to you - This feature helps to update only the relevant property of a segment definition without copying the complex PQL of the segment. 

How would you like the feature to work -  The patch solution should have been like Field Group "Patch" API call. Just what property we need to replace and the corresponding value. 

{

    "op": "replace",

    "path": "/mergePolicyId",

        "value": "<revised Merge Policy ID>"

}

Current Behaviour - 

The Update API call requires entire definition of the segment along with PQL and other properties to be part of payload while changing the properties like merge policy etc.