Caching strategy

[timlinux]

@NyakudyaA So I . have been thinking about how to make things performant and I think this will be a good strategy:

We cache the 'blueprint' layers as a layer group:

If needed, attach some external storage to the server to host the tiles.

Then for the dynamic requests (flooded buildings etc.) we can use a different colour scheme (see #34 ) and simply draw those buildings over the top of the blueprint layer.

See also #37

[NyakudyaA]

@timlinux I have already enabled caching for all the layers so as we render them they will be cached.
So currently the way things are working is.

• osm_buildings, osm_roads, osm_waterways are being cached.
• When a user draws a flood polygon all the intersects are coming from a different view that has already been published using the same style (will need to change this).

I also plan to add a separate container in rancher that does the following.

• Empty geowebcache every friday @11pm
• Regenerate the cache to get new data.