[web UI] subnet settings are dangerously easy to change

[Peter Matulis]

In the web UI, when a subnet is clicked upon its window opens and fields in the summary section are immediately editable and changes are applied immediately (there is no Save button). Not only is this dangerous (because it's unexpected) but it is also inconsistent with the rest of the UI. A node's window, for instance, can be opened but the user must hit the Edit button in order to make changes and then Save to apply those changes.