Add API to use 3D Widget representations within pvweb

Change-Id: I77d7794b08379482d0b936e9f1dfea237580a4a2
Merge master into next

Change-Id: Ic9bf75f26d5424c0fb4183d5105bd7817f78d17c
Merge topic 'pvweb-add-widget-support' into next

17089e51 Add API to use 3D Widget representations within pvweb