chore(assets): add startup_benchmark image

This image was generated from a comparison between the largetable-bp benchmark from
the angular tree between 1.3.0-rc.1 (actually a few commits ahead of rc1), and 1.2.24,
using the interpolate mode.

We see about 1/3 of the startup time chopped right off, which is a big deal
chore(presentation): reorganize more slides