Integrate node creation and deletion with server

[reddigari]

• Hits new workspace endpoint on page load
• Hits new node endpoint on node drag-and-drop
• Hits delete node endpoint on node deletion
• Fixes the data the server sends to populate node menu

Error handling is minimal, but I try to check most server responses and log non-200s to the console for now. Next up is a banner or something that displays error messages (which the server already sends).