Show how to get/set thumbnail photo

[dkershaw10]

Add this to the sample.

[vvolodin]

The sample's description says:

This console application is a .Net sample, using the Graph API Client library (Version 2.0) - it demonstrates common Read calls to the Graph API including Getting Users, Groups, Group Membership, Roles, Tenant information, Service Principals, Applications. The second part of the sample app demonstrates common Write/Update/Delete options on Users, Groups, and shows how to execute User License Assignment, updating a User's thumbnailPhoto and links, etc. It also can read the contents from the signed-on user's mailbox.

Why are thumbnailPhoto functions missing?