[Observium] Ports page performance

Hi All,

I've made some changes to how the ports page works to try to improve performance for people with very large installations.

If you have issues with the /ports/ page speed, please test the speed of your install by loading /ports/, and trying with 1000 and 10000 ports page sizes. You need to refresh each page a few times to get an accurate page generation time. (the page generation time is at the bottom left) Then update your install with 'svn up' and run the same tests again. Please report back how much performance improvement you see, if any.

I've also reduced some of the field sizes for the ports-state table which should reduce MySQL heap usage by about 20%.

Thanks, adam.