Part of #8518Closes#8822
The drop downs were missing, because WidgetFunction had a higher score than them and took precedence. The fix was to adjust scores, so drop down is before both argument name and function. Generally, any widget expecting to "overlap" existing code (and possibly further widgets) should go before WidgetFunction.
# Important Notes
* Extended mockExpressionUpdate to accept a subexpression of a node. Also, I removed it from GraphDb - I want this function to have as little impact on app code as possible.
