Hide sprite initially
Remove the Sensing tab
Fix whitespace in changesToStore.js
Add password-protected custom blocks

Thanks to @Craxic for providing most of the implementation.
Split Graph tab into Graph and Nodes+edges
Reorder blocks in tabs
Fix typo in 'edges with attribute %s equal to %s'
Move node/edge existence into Graph tab
Rename Graph tab to Network
Add 'is empty' predicate