New students updates global objects, can cause re-rendering of activity types

[houshuang]

Currently it seems that every time a new student is added to a graph, the globalObject of the currently open activity is modified, this causes an update message to all clients, and in some cases a re-rendering of the current activity, which can lead to losing focus in li-richText.

1 - Do any activities need access to globalObject, or should we stop sending it?
2 - Make activities more resilient to new data?