webui: server-side sectors page rendering

[magik6k]

Not quite done, but it does render and make paginated requests.

TODO

• Terminate/etc buttons are gone
• Backend requests are still quite slow, some queries most likely need optimizing (likely all the total count stuff)
• Data doesn't start loading until scrolling is stopped which feels a little janky. Likely a DataTables setting

Relevant docs https://datatables.net/manual/server-side