UrlSync: Started exploring improvements

[torkelo]

Started exploring some url sync changes

• Always include full url state in updateFromUrl not only changed values

Other things I want to fix

• Support scene objects added later after initial url sync still being able to read state from URL
• Fix timing issue where state change during updateFromUrl that triggers another url sync should break the current url sync so that the first url sync does not overwrite the state of a later update. Still not been able to create a unit test for this. Timing issue should be fixed by UrlSync: Fixes overwrite issue where later state change overwrites earlier change #555

Problem

• some of these changes (esp the first) could create subtle new bugs (and potentially recursive update loops).