Improvements and fixes

The day power curve reads correctly again, a plant's VPN assignment takes several subnets, and pages no longer stall while logging.

• The day power curve's forecast no longer detaches from the production line, and its last 15 minutes no longer jump between meter and inverter values.
• Assigning a plant to a VPN service takes several subnets: add or remove rows in the dialog, and duplicates are rejected.
• The plants table's VPN dialog preselects the VPN service that plant is assigned to, instead of the first service with plants.
• Pages no longer stall while the app records its troubleshooting log in your browser; that log is now kept in a compact form.