Small improvements to docs

[cmutel]

IMHO, you could:

• Slow down the video a bit when doing data entry, as it is hard for us old folk to see
• Put the video in the section on "Using LCOPT", as a concrete example (this section doesn't have much on the actual use of the software so far).

[pjamesjoyce]

Looking back at the video you're absolutely right! I've slowed it down and added some more descriptive captions relating to the data entry. It's now more of a how-to video - it was previously more showcasing what it could do.

I've also moved the video to the newly created Getting Started section and made a couple of edits to the Using Lcopt section.

I'll leave this open for you to close if you're happy with the updates.

[pjamesjoyce]

Link this issue to openjournals/joss-reviews#339