On GH defintion open, update is sent needlessly

[didimitrie]

Step 0:

• I've read the contribution guidelines!

Actual Behaviour

When you open a GH defintion with SpeckleSenders inside, they all send out an initial update.

Proposed Solution (if any)

Set up a flag on document open and prevent the initial update, if possible. Otherwise, maybe hash the stream's last state and compare, if equivalent, do not send update.

[didimitrie]

closed, dupe