Pre-warm cache on demo boot up

[chillu]

Overview

As a product owner, I want the very first request to be as fast as possible to make a good fist impression on the demo user.

SilverStripe builds an in-memory cache on the first request, mostly for templates. This normally only happens on the very first request and takes but a fraction of a second, so we normally don't worry about it too much. However, this very first request will be served to the user having requested a demo and this will be their very first impression of SilverStripe.

Acceptance criteria

• Common entry points into the SilverStripe demo have their cache pre-warmed.