SpeckleObject doesn't have Duplicate()

[tsvilans]

Step 0:

• [x] I've read the contribution guidelines!

Expected Behaviour

SpeckleObject should have a Duplicate() method.

Actual Behaviour

It doesn't.

Affected Projects

Projects where you want to duplicate a SpeckleObject.

Reproduction Steps & System Config (win, osx, web, etc.)

Try to use SpeckleObject.Duplicate()

Proposed Solution (if any)

Implement Duplicate() for SpeckleObjects.