Time controls: heatmap

[sbrl]

The heatmap also needs a time control on it, but I suspect it'll end working very differently to the device graph.

• Re-investigate leaflet-timedimension
• Get bounds from PHP API
• Fetch new heatmap data and display it based on leaflet-timedimension event

[sbrl]

We've made progress here & rolled out some controls, but we've got some performance issues to deal with. We should track those down & maybe alter the UI a bit to make it easier to select a time (it's only going to get harder as we generate more data lol :P) before closing this issue.

[sbrl]

With respect to the performance issues, it's possible that the Apache server that's hosting the web interface isn't using FastCGI, instead opting for the (much) slower CGI. We'll have to investigate.

• Check that the server is using FastCGI
• Investigate possibility of using PHP-FPM
• Add server-side caching layer for output of appropriate actions
• Consider using a separate server(?) with Nginx if we need more speed?

To be honest though, we really need to fix #30 first though. It's a seriously nasty bug that may result in us moving to a different plugin :-/

[sbrl]

Bother it all. With the new heatmap implementation, we're back to square 1 with this issue.

Thankfully, the performance issues have been somewhat alleviated by the squashing of a bunch of nasty datetime format warnings. We'll see how much of a difference this'll make to a fancy animation time controls system when we get around to implementing this again.

We'll probably have to do something about the leaflet-timedimension default UI though, because its; not exactly suitable for our usage. Maybe a calendar & clock or something might work, with some arrows to jump forwards & backwards by set amounts (6 minutes, 1 hour, 1 day, custom, etc.?) might work?

Thought it needed.