[OSGeoLive] MapSlicer QuickStart review (Season of Docs)

[Felicity Brand]

Hello,

I have completed my second QuickStart review. Still ironing out the
process so do let me know any feedback.

I have created a PR on GitHub: https://github.com/OSGeo/OSGeoLive-doc/pull/517
And I have created its partner ticket in trac:
https://trac.osgeo.org/osgeolive/ticket/2188#ticket

If the comments on this one are too convoluted to follow, let me know
and I can explain further or show you what I'm thinking.

Thanks
Felicity